Permalink
2228 lines (1716 sloc) 75.9 KB
defmodule Ecto.Schema do
@moduledoc ~S"""
Defines a schema.
An Ecto schema is used to map any data source into an Elixir struct.
The definition of the schema is possible through two main APIs:
`schema/2` and `embedded_schema/1`.
`schema/2` is typically used to map data from a persisted source,
usually a database table, into Elixir structs and vice-versa. For
this reason, the first argument of `schema/2` is the source (table)
name. Structs defined with `schema/2` also contain a `__meta__` field
with metadata holding the status of the struct, for example, if it
has been built, loaded or deleted.
On the other hand, `embedded_schema/1` is used for defining schemas
that are embedded in other schemas or only exist in-memory. For example,
you can use such schemas to receive data from a command line interface
and validate it, without ever persisting it elsewhere. Such structs
do not contain a `__meta__` field, as they are never persisted.
Besides working as data mappers, `embedded_schema/1` and `schema/2` can
also be used together to decouple how the data is represented in your
applications from the database. Let's see some examples.
## Example
defmodule User do
use Ecto.Schema
schema "users" do
field :name, :string
field :age, :integer, default: 0
has_many :posts, Post
end
end
By default, a schema will automatically generate a primary key which is named
`id` and of type `:integer`. The `field` macro defines a field in the schema
with given name and type. `has_many` associates many posts with the user
schema. Schemas are regular structs and can be created and manipulated directly
using Elixir's struct API:
iex> user = %User{name: "jane"}
iex> %{user | age: 30}
However, most commonly, structs are cast, validated and manipulated with the
`Ecto.Changeset` module.
Note that the name of the database table does not need to correlate to your
module name. For example, if you are working with a legacy database, you can
reference the table name when you define your schema:
defmodule User do
use Ecto.Schema
schema "legacy_users" do
# ... fields ...
end
end
Embedded schemas are defined similarly to source-based schemas. For example,
you can use an embedded schema to represent your UI, mapping and validating
its inputs, and then you convert such embedded schema to other schemas that
are persisted to the database:
defmodule SignUp do
use Ecto.Schema
embedded_schema do
field :name, :string
field :age, :integer
field :email, :string
field :accepts_conditions, :boolean
end
end
defmodule Profile do
use Ecto.Schema
schema "profiles" do
field :name
field :age
belongs_to :account, Account
end
end
defmodule Account do
use Ecto.Schema
schema "accounts" do
field :email
end
end
The `SignUp` schema can be cast and validated with the help of the
`Ecto.Changeset` module, and afterwards, you can copy its data to
the `Profile` and `Account` structs that will be persisted to the
database with the help of `Ecto.Repo`.
## Schema attributes
Supported attributes, to be set beforehand, for configuring the defined schema.
These attributes are:
* `@primary_key` - configures the schema primary key. It expects
a tuple `{field_name, type, options}` with the primary key field
name, type (typically `:id` or `:binary_id`, but can be any type) and
options. Defaults to `{:id, :id, autogenerate: true}`. When set
to `false`, does not define a primary key in the schema unless
composite keys are defined using the options of `field`.
* `@schema_prefix` - configures the schema prefix. Defaults to `nil`,
which generates structs and queries without prefix. When set, the
prefix will be used by every built struct and on queries whenever
the schema is used in a `from` or a `join`. In PostgreSQL, the prefix
is called "SCHEMA" (typically set via Postgres' `search_path`).
In MySQL the prefix points to databases.
* `@foreign_key_type` - configures the default foreign key type
used by `belongs_to` associations. Defaults to `:id`;
* `@timestamps_opts` - configures the default timestamps type
used by `timestamps`. Defaults to `[type: :naive_datetime]`;
* `@derive` - the same as `@derive` available in `Kernel.defstruct/1`
as the schema defines a struct behind the scenes;
* `@field_source_mapper` - a function that receives the current field name
and returns the mapping of this field name in the underlying source.
In other words, it is a mechanism to automatically generate the `:source`
option for the `field` macro. It defaults to `fn x -> x end`, where no
field transformation is done;
The advantage of configuring the schema via those attributes is
that they can be set with a macro to configure application wide
defaults.
For example, if your database does not support autoincrementing
primary keys and requires something like UUID or a RecordID, you
can configure and use`:binary_id` as your primary key type as follows:
# Define a module to be used as base
defmodule MyApp.Schema do
defmacro __using__(_) do
quote do
use Ecto.Schema
@primary_key {:id, :binary_id, autogenerate: true}
@foreign_key_type :binary_id
end
end
end
# Now use MyApp.Schema to define new schemas
defmodule MyApp.Comment do
use MyApp.Schema
schema "comments" do
belongs_to :post, MyApp.Post
end
end
Any schemas using `MyApp.Schema` will get the `:id` field with type
`:binary_id` as the primary key. We explain what the `:binary_id` type
entails in the next section.
The `belongs_to` association on `MyApp.Comment` will also define
a `:post_id` field with `:binary_id` type that references the `:id`
field of the `MyApp.Post` schema.
## Primary keys
Ecto supports two ID types, called `:id` and `:binary_id`, which are
often used as the type for primary keys and associations.
The `:id` type is used when the primary key is an integer while the
`:binary_id` is used for primary keys in particular binary formats,
which may be `Ecto.UUID` for databases like PostgreSQL and MySQL,
or some specific ObjectID or RecordID often imposed by NoSQL databases.
In both cases, both types have their semantics specified by the
underlying adapter/database. If you use the `:id` type with
`:autogenerate`, it means the database will be responsible for
auto-generation of the id. This is often the case for primary keys
in relational databases which are auto-incremented.
Similarly, the `:binary_id` type may be generated in the adapter
for cases like UUID but it may also be handled by the database if
required. In any case, both scenarios are handled transparently by
Ecto.
Besides `:id` and `:binary_id`, which are often used by primary
and foreign keys, Ecto provides a huge variety of types to be used
by any column.
Ecto also supports composite primary keys.
If your primary key is not named "id" (e.g. if you are working with a
legacy database), you can use the `@primary_key` attribute to configure
your key name using the `source` option. For example, the following
attribute defines an integer primary key named `legacy_id` which is
automatically incremented by the database:
@primary_key {:id, :integer, autogenerate: false, source: :legacy_id}
## Types and casting
When defining the schema, types need to be given. Types are split
into two categories, primitive types and custom types.
### Primitive types
The primitive types are:
Ecto type | Elixir type | Literal syntax in query
:---------------------- | :---------------------- | :---------------------
`:id` | `integer` | 1, 2, 3
`:binary_id` | `binary` | `<<int, int, int, ...>>`
`:integer` | `integer` | 1, 2, 3
`:float` | `float` | 1.0, 2.0, 3.0
`:boolean` | `boolean` | true, false
`:string` | UTF-8 encoded `string` | "hello"
`:binary` | `binary` | `<<int, int, int, ...>>`
`{:array, inner_type}` | `list` | `[value, value, value, ...]`
`:map` | `map` |
`{:map, inner_type}` | `map` |
`:decimal` | [`Decimal`](https://github.com/ericmj/decimal) |
`:date` | `Date` |
`:time` | `Time` |
`:naive_datetime` | `NaiveDateTime` |
`:naive_datetime_usec` | `NaiveDateTime` |
`:utc_datetime` | `DateTime` |
`:utc_datetime_usec` | `DateTime` |
**Notes:**
* For the `{:array, inner_type}` and `{:map, inner_type}` type,
replace `inner_type` with one of the valid types, such as `:string`.
* For the `:decimal` type, `+Infinity`, `-Infinity`, and `NaN` values
are not supported, even though the `Decimal` library handles them.
To support them, you can create a custom type.
* For calendar types with and without microseconds, the precision is
enforced when persisting to the DB. For example, casting `~T[09:00:00]`
as `:time_usec` will succeed and result in `~T[09:00:00.000000]`, but
persisting a type without microseconds as `:time_usec` will fail.
Similarly, casting `~T[09:00:00.000000]` as `:time` will succeed, but
persisting will not. This is the same behaviour as seen in other types,
where casting has to be done explicitly and is never performed
implicitly when loading from or dumping to the database.
### Custom types
Besides providing primitive types, Ecto allows custom types to be
implemented by developers, allowing Ecto behaviour to be extended.
A custom type is a module that implements the `Ecto.Type` behaviour.
By default, Ecto provides the following custom types:
Custom type | Database type | Elixir type
:---------------------- | :---------------------- | :---------------------
`Ecto.UUID` | `:uuid` | `uuid-string`
Read the `Ecto.Type` documentation for more information on implementing
your own types.
Finally, schemas can also have virtual fields by passing the
`virtual: true` option. These fields are not persisted to the database
and can optionally not be type checked by declaring type `:any`.
### The datetime types
Four different datetime primitive types are available:
* `naive_datetime` - has a precision of seconds and casts values
to Elixir's `NaiveDateTime` struct which has no timezone information.
* `naive_datetime_usec` - has a default precision of microseconds and
also casts values to `NaiveDateTime` with no timezone information.
* `utc_datetime` - has a precision of seconds and casts values to
to Elixir's `DateTime` struct and expects the time zone to be set to UTC.
* `utc_datetime_usec` has a default precision of microseconds and also
casts values to `DateTime` expecting the time zone be set to UTC.
Having these different types allows developers to choose a type that will
be compatible with the database and your project's precision requirements.
For example, some older versions of MySQL do not support microseconds in
datetime fields.
When choosing what datetime type to work with, keep in mind that Elixir
functions like `NaiveDateTime.utc_now/0` have a default precision of 6.
Casting a value with a precision greater than 0 to a non-`usec` type will
truncate all microseconds and set the precision to 0.
### The map type
The map type allows developers to store an Elixir map directly
in the database:
# In your migration
create table(:users) do
add :data, :map
end
# In your schema
field :data, :map
# Now in your code
user = Repo.insert! %User{data: %{"foo" => "bar"}}
Keep in mind that we advise the map keys to be strings or integers
instead of atoms. Atoms may be accepted depending on how maps are
serialized but the database will always convert atom keys to strings
due to security reasons.
In order to support maps, different databases may employ different
techniques. For example, PostgreSQL will store those values in jsonb
fields, allowing you to just query parts of it. MySQL and MSSQL, on
the other hand, do not yet provide a JSON type, so the value will be
stored in a text field.
For maps to work in such databases, Ecto will need a JSON library.
By default Ecto will use [Jason](http://github.com/michalmuskala/jason)
which needs to be added to your deps in `mix.exs`:
{:jason, "~> 1.0"}
You can however configure the adapter to use another library. For example,
if using Postgres:
config :postgrex, :json_library, YourLibraryOfChoice
Or if using MySQL:
config :mariaex, :json_library, YourLibraryOfChoice
If changing the JSON library, remember to recompile the adapter afterwards
by cleaning the current build:
mix deps.clean --build postgrex
### Casting
When directly manipulating the struct, it is the responsibility of
the developer to ensure the field values have the proper type. For
example, you can create a user struct with an invalid value
for `age`:
iex> user = %User{age: "0"}
iex> user.age
"0"
However, if you attempt to persist the struct above, an error will
be raised since Ecto validates the types when sending them to the
adapter/database.
Therefore, when working with and manipulating external data, it is
recommended to use `Ecto.Changeset`'s that are able to filter
and properly cast external data:
changeset = Ecto.Changeset.cast(%User{}, %{"age" => "0"}, [:age])
user = Repo.insert!(changeset)
**You can use Ecto schemas and changesets to cast and validate any kind
of data, regardless if the data will be persisted to an Ecto repository
or not**.
## Reflection
Any schema module will generate the `__schema__` function that can be
used for runtime introspection of the schema:
* `__schema__(:source)` - Returns the source as given to `schema/2`;
* `__schema__(:prefix)` - Returns optional prefix for source provided by
`@schema_prefix` schema attribute;
* `__schema__(:primary_key)` - Returns a list of primary key fields (empty if there is none);
* `__schema__(:fields)` - Returns a list of all non-virtual field names;
* `__schema__(:field_source, field)` - Returns the alias of the given field;
* `__schema__(:type, field)` - Returns the type of the given non-virtual field;
* `__schema__(:associations)` - Returns a list of all association field names;
* `__schema__(:association, assoc)` - Returns the association reflection of the given assoc;
* `__schema__(:embeds)` - Returns a list of all embedded field names;
* `__schema__(:embed, embed)` - Returns the embedding reflection of the given embed;
* `__schema__(:read_after_writes)` - Non-virtual fields that must be read back
from the database after every write (insert or update);
* `__schema__(:autogenerate_id)` - Primary key that is auto generated on insert;
Furthermore, both `__struct__` and `__changeset__` functions are
defined so structs and changeset functionalities are available.
"""
@type source :: String.t
@type prefix :: String.t | nil
@type schema :: %{optional(atom) => any, __struct__: atom, __meta__: Ecto.Schema.Metadata.t}
@type embedded_schema :: %{optional(atom) => any, __struct__: atom}
@type t :: schema | embedded_schema
defmodule Metadata do
@moduledoc """
Stores metadata of a struct.
## State
The state of the schema is stored in the `:state` field and allows
following values:
* `:built` - the struct was constructed in memory and is not persisted
to database yet;
* `:loaded` - the struct was loaded from database and represents
persisted data;
* `:deleted` - the struct was deleted and no longer represents persisted
data.
## Source
The `:source` tracks the (table or collection) where the struct is or should
be persisted to.
## Prefix
Tracks the source prefix in the data storage.
## Context
The `:context` field represents additional state some databases require
for proper updates of data. It is not used by the built-in adapters of
`Ecto.Adapters.Postres` and `Ecto.Adapters.MySQL`.
## Schema
The `:schema` field refers the module name for the schema this metadata belongs to.
"""
defstruct [:state, :source, :context, :schema, :prefix]
@type state :: :built | :loaded | :deleted
@type t :: %__MODULE__{
context: any,
prefix: Ecto.Schema.prefix,
schema: module,
source: Ecto.Schema.source,
state: state,
}
defimpl Inspect do
import Inspect.Algebra
def inspect(metadata, opts) do
%{source: source, prefix: prefix, state: state, context: context} = metadata
entries =
for entry <- [state, prefix, source, context],
entry != nil,
do: to_doc(entry, opts)
concat ["#Ecto.Schema.Metadata<"] ++ Enum.intersperse(entries, ", ") ++ [">"]
end
end
end
@doc false
defmacro __using__(_) do
quote do
import Ecto.Schema, only: [schema: 2, embedded_schema: 1]
@primary_key nil
@timestamps_opts []
@foreign_key_type :id
@schema_prefix nil
@field_source_mapper fn x -> x end
Module.register_attribute(__MODULE__, :ecto_primary_keys, accumulate: true)
Module.register_attribute(__MODULE__, :ecto_fields, accumulate: true)
Module.register_attribute(__MODULE__, :ecto_field_sources, accumulate: true)
Module.register_attribute(__MODULE__, :ecto_assocs, accumulate: true)
Module.register_attribute(__MODULE__, :ecto_embeds, accumulate: true)
Module.register_attribute(__MODULE__, :ecto_raw, accumulate: true)
Module.register_attribute(__MODULE__, :ecto_autogenerate, accumulate: true)
Module.register_attribute(__MODULE__, :ecto_autoupdate, accumulate: true)
Module.put_attribute(__MODULE__, :ecto_autogenerate_id, nil)
end
end
@doc """
Defines an embedded schema with the given field definitions.
An embedded schema is either embedded into another
schema or kept exclusively in memory. For this reason,
an embedded schema does not require a source name and
it does not include a metadata field.
Embedded schemas by default set the primary key type
to `:binary_id` but such can be configured with the
`@primary_key` attribute.
"""
defmacro embedded_schema([do: block]) do
schema(nil, false, :binary_id, block)
end
@doc """
Defines a schema struct with a source name and field definitions.
An additional field called `__meta__` is added to the struct for storing
internal Ecto state. This field always has a `Ecto.Schema.Metadata` struct
as value and can be manipulated with the `Ecto.put_meta/2` function.
"""
defmacro schema(source, [do: block]) do
schema(source, true, :id, block)
end
defp schema(source, meta?, type, block) do
prelude =
quote do
@after_compile Ecto.Schema
Module.register_attribute(__MODULE__, :changeset_fields, accumulate: true)
Module.register_attribute(__MODULE__, :struct_fields, accumulate: true)
meta? = unquote(meta?)
source = unquote(source)
prefix = @schema_prefix
# Those module attributes are accessed only dynamically
# so we explicitly reference them here to avoid warnings.
_ = @foreign_key_type
_ = @timestamps_opts
if meta? do
unless is_binary(source) do
raise ArgumentError, "schema source must be a string, got: #{inspect source}"
end
meta = %Metadata{state: :built, source: source, prefix: prefix, schema: __MODULE__}
Module.put_attribute(__MODULE__, :struct_fields, {:__meta__, meta})
end
if @primary_key == nil do
@primary_key {:id, unquote(type), autogenerate: true}
end
primary_key_fields =
case @primary_key do
false ->
[]
{name, type, opts} ->
Ecto.Schema.__field__(__MODULE__, name, type, [primary_key: true] ++ opts)
[name]
other ->
raise ArgumentError, "@primary_key must be false or {name, type, opts}"
end
try do
import Ecto.Schema
unquote(block)
after
:ok
end
end
postlude =
quote unquote: false do
primary_key_fields = @ecto_primary_keys |> Enum.reverse
autogenerate = @ecto_autogenerate |> Enum.reverse
autoupdate = @ecto_autoupdate |> Enum.reverse
fields = @ecto_fields |> Enum.reverse
field_sources = @ecto_field_sources |> Enum.reverse
assocs = @ecto_assocs |> Enum.reverse
embeds = @ecto_embeds |> Enum.reverse
defstruct @struct_fields
def __changeset__ do
%{unquote_splicing(Macro.escape(@changeset_fields))}
end
def __schema__(:prefix), do: unquote(prefix)
def __schema__(:source), do: unquote(source)
def __schema__(:fields), do: unquote(Enum.map(fields, &elem(&1, 0)))
def __schema__(:primary_key), do: unquote(primary_key_fields)
def __schema__(:hash), do: unquote(:erlang.phash2({primary_key_fields, fields}))
def __schema__(:read_after_writes), do: unquote(Enum.reverse(@ecto_raw))
def __schema__(:autogenerate_id), do: unquote(Macro.escape(@ecto_autogenerate_id))
def __schema__(:autogenerate), do: unquote(Macro.escape(autogenerate))
def __schema__(:autoupdate), do: unquote(Macro.escape(autoupdate))
def __schema__(:query) do
%Ecto.Query{
from: %Ecto.Query.FromExpr{
source: {unquote(source), __MODULE__},
prefix: unquote(prefix)
}
}
end
for clauses <- Ecto.Schema.__schema__(fields, field_sources, assocs, embeds),
{args, body} <- clauses do
def __schema__(unquote_splicing(args)), do: unquote(body)
end
end
quote do
unquote(prelude)
unquote(postlude)
end
end
## API
@doc """
Defines a field on the schema with given name and type.
The field name will be used as is to read and write to the database
by all of the built-in adapters unless overridden with the `:source`
option.
## Options
* `:default` - Sets the default value on the schema and the struct.
The default value is calculated at compilation time, so don't use
expressions like `DateTime.utc_now` or `Ecto.UUID.generate` as
they would then be the same for all records.
* `:source` - Defines the name that is to be used in database for this field.
This is useful when attaching to an existing database. The value should be
an atom.
* `:autogenerate` - a `{module, function, args}` tuple for a function
to call to generate the field value before insertion if value is not set.
A shorthand value of `true` is equivalent to `{type, :autogenerate, []}`.
* `:read_after_writes` - When true, the field is always read back
from the database after insert and updates.
For relational databases, this means the RETURNING option of those
statements is used. For this reason, MySQL does not support this
option and will raise an error if a schema is inserted/updated with
read after writes fields.
* `:virtual` - When true, the field is not persisted to the database.
Notice virtual fields do not support `:autogenerate` nor
`:read_after_writes`.
* `:primary_key` - When true, the field is used as part of the
composite primary key
"""
defmacro field(name, type \\ :string, opts \\ []) do
quote do
Ecto.Schema.__field__(__MODULE__, unquote(name), unquote(type), unquote(opts))
end
end
@doc """
Generates `:inserted_at` and `:updated_at` timestamp fields.
The fields generated by this macro will automatically be set to
the current time when inserting and updating values in a repository.
## Options
* `:type` - the timestamps type, defaults to `:naive_datetime`.
* `:inserted_at` - the name of the column for insertion times or `false`
* `:updated_at` - the name of the column for update times or `false`
* `:autogenerate` - a module-function-args tuple used for generating
both `inserted_at` and `updated_at` timestamps
All options can be pre-configured by setting `@timestamps_opts`.
"""
defmacro timestamps(opts \\ []) do
quote bind_quoted: binding() do
timestamps =
[inserted_at: :inserted_at, updated_at: :updated_at, type: :naive_datetime]
|> Keyword.merge(@timestamps_opts)
|> Keyword.merge(opts)
type = Keyword.fetch!(timestamps, :type)
autogen = timestamps[:autogenerate] || {Ecto.Schema, :__timestamps__, [type]}
if inserted_at = Keyword.fetch!(timestamps, :inserted_at) do
Ecto.Schema.field(inserted_at, type, [])
Module.put_attribute(__MODULE__, :ecto_autogenerate, {inserted_at, autogen})
end
if updated_at = Keyword.fetch!(timestamps, :updated_at) do
Ecto.Schema.field(updated_at, type, [])
Module.put_attribute(__MODULE__, :ecto_autogenerate, {updated_at, autogen})
Module.put_attribute(__MODULE__, :ecto_autoupdate, {updated_at, autogen})
end
end
end
@doc ~S"""
Indicates a one-to-many association with another schema.
The current schema has zero or more records of the other schema. The other
schema often has a `belongs_to` field with the reverse association.
## Options
* `:foreign_key` - Sets the foreign key, this should map to a field on the
other schema, defaults to the underscored name of the current schema
suffixed by `_id`
* `:references` - Sets the key on the current schema to be used for the
association, defaults to the primary key on the schema
* `:through` - Allow this association to be defined in terms of existing
associations. Read the section on `:through` associations for more info
* `:on_delete` - The action taken on associations when parent record
is deleted. May be `:nothing` (default), `:nilify_all` and `:delete_all`.
Notice `:on_delete` may also be set in migrations when creating a
reference. If your database supports it, setting the `:on_delete` in the
migration is preferred as the database can effectively guarantee integrity,
it is more efficient, and it also allows `:nilify_all` and `:delete_all`
to cascade.
* `:on_replace` - The action taken on associations when the record is
replaced when casting or manipulating parent changeset. May be
`:raise` (default), `:mark_as_invalid`, `:nilify`, or `:delete`.
See `Ecto.Changeset`'s section on related data for more info.
* `:defaults` - Default values to use when building the association
* `:where` - A filter for the association. See "Filtering associations" below.
It does not apply to `:through` associations.
## Examples
defmodule Post do
use Ecto.Schema
schema "posts" do
has_many :comments, Comment
end
end
# Get all comments for a given post
post = Repo.get(Post, 42)
comments = Repo.all assoc(post, :comments)
# The comments can come preloaded on the post struct
[post] = Repo.all(from(p in Post, where: p.id == 42, preload: :comments))
post.comments #=> [%Comment{...}, ...]
`has_many` can be used to define hierarchical relationships within a single
schema, for example threaded comments.
defmodule Comment do
use Ecto.Schema
schema "comments" do
field :content, :string
field :parent_id, :integer
belongs_to :parent, Comment, foreign_key: :id, references: :parent_id, define_field: false
has_many :children, Comment, foreign_key: :parent_id, references: :id
end
end
## Filtering associations
A query can also be given instead of a schema. Querying, joining or preloading
the association will use the given query. Currently only where clauses can be
provided in queries. Let's see some examples:
defmodule Post do
use Ecto.Schema
schema "posts" do
has_many :public_comments, Comment,
where: [public: true]
has_many :deleted_comments, Comment,
where: dynamic([c], not(is_nil(comment.deleted_at)))
end
end
The `:where` option may receive a dynamic query, a keyword list or a MFA
(a tuple with a module, function and args to invoke). The MFA is especially
useful to avoid duplication in those definitions:
defmodule Comment do
def deleted_filter do
dynamic([c], not(is_nil(comment.deleted_at)))
end
end
defmodule Post do
use Ecto.Schema
schema "posts" do
has_many :deleted_comments, Comment,
where: {Comment, :deleted_filter, []}
end
end
**Important!** Please use this feature only when strictly necessary,
otherwise it is very easy to end-up with large schemas with dozens of
different associations polluting your schema and affecting your
application performance. For instance, if you are using associations
only for different querying purposes, then it is preferable to build
and compose queries, rather than defining multiple associations:
posts
|> Ecto.assoc(:comments)
|> Comment.deleted()
Or when preloading:
from posts, preload: [comments: ^Comment.deleted()]
## has_many/has_one :through
Ecto also supports defining associations in terms of other associations
via the `:through` option. Let's see an example:
defmodule Post do
use Ecto.Schema
schema "posts" do
has_many :comments, Comment
has_one :permalink, Permalink
# In the has_many :through example below, the `:comments`
# in the list [:comments, :author] refers to the
# `has_many :comments` in the Post own schema and the
# `:author` refers to the `belongs_to :author` of the
# Comment's schema (the module below).
# (see the description below for more details)
has_many :comments_authors, through: [:comments, :author]
# Specify the association with custom source
has_many :tags, {"posts_tags", Tag}
end
end
defmodule Comment do
use Ecto.Schema
schema "comments" do
belongs_to :author, Author
belongs_to :post, Post
has_one :post_permalink, through: [:post, :permalink]
end
end
In the example above, we have defined a `has_many :through` association
named `:comments_authors`. A `:through` association always expects a list
and the first element of the list must be a previously defined association
in the current module. For example, `:comments_authors` first points to
`:comments` in the same module (Post), which then points to `:author` in
the next schema, `Comment`.
This `:through` association will return all authors for all comments
that belongs to that post:
# Get all comments authors for a given post
post = Repo.get(Post, 42)
authors = Repo.all assoc(post, :comments_authors)
Although we used the `:through` association in the example above, Ecto
also allows developers to dynamically build the through associations using
the `Ecto.assoc/2` function:
assoc(post, [:comments, :author])
In fact, given `:through` associations are read-only, **using the `Ecto.assoc/2`
format is the preferred mechanism for working with through associations**. Use
the schema-based one only if you need to store the through data alongside of
the parent struct, in specific cases such as preloading.
`:through` associations can also be preloaded. In such cases, not only
the `:through` association is preloaded but all intermediate steps are
preloaded too:
[post] = Repo.all(from(p in Post, where: p.id == 42, preload: :comments_authors))
post.comments_authors #=> [%Author{...}, ...]
# The comments for each post will be preloaded too
post.comments #=> [%Comment{...}, ...]
# And the author for each comment too
hd(post.comments).author #=> %Author{...}
When the `:through` association is expected to return one or zero items,
`has_one :through` should be used instead, as in the example at the beginning
of this section:
# How we defined the association above
has_one :post_permalink, through: [:post, :permalink]
# Get a preloaded comment
[comment] = Repo.all(Comment) |> Repo.preload(:post_permalink)
comment.post_permalink #=> %Permalink{...}
"""
defmacro has_many(name, queryable, opts \\ []) do
queryable = expand_alias(queryable, __CALLER__)
quote do
Ecto.Schema.__has_many__(__MODULE__, unquote(name), unquote(queryable), unquote(opts))
end
end
@doc ~S"""
Indicates a one-to-one association with another schema.
The current schema has zero or one records of the other schema. The other
schema often has a `belongs_to` field with the reverse association.
## Options
* `:foreign_key` - Sets the foreign key, this should map to a field on the
other schema, defaults to the underscored name of the current module
suffixed by `_id`
* `:references` - Sets the key on the current schema to be used for the
association, defaults to the primary key on the schema
* `:through` - If this association must be defined in terms of existing
associations. Read the section in `has_many/3` for more information
* `:on_delete` - The action taken on associations when parent record
is deleted. May be `:nothing` (default), `:nilify_all` and `:delete_all`.
Notice `:on_delete` may also be set in migrations when creating a
reference. If your database supports it, setting the `:on_delete` in the
migration is preferred as the database can effectively guarantee integrity,
it is more efficient, and it also allows `:nilify_all` and `:delete_all`
to cascade.
* `:on_replace` - The action taken on associations when the record is
replaced when casting or manipulating parent changeset. May be
`:raise` (default), `:mark_as_invalid`, `:nilify`, `:update`, or
`:delete`. See `Ecto.Changeset`'s section on related data for more info.
* `:defaults` - Default values to use when building the association
* `:where` - A filter for the association. See "Filtering associations"
in `has_many/3`. It does not apply to `:through` associations.
## Examples
defmodule Post do
use Ecto.Schema
schema "posts" do
has_one :permalink, Permalink
# Specify the association with custom source
has_one :category, {"posts_categories", Category}
end
end
# The permalink can come preloaded on the post struct
[post] = Repo.all(from(p in Post, where: p.id == 42, preload: :permalink))
post.permalink #=> %Permalink{...}
## Using Queries as Associations
A query can also be given instead of a schema. Querying, joining or preloading the association will
use the given query. Currently only where clauses can be provided in queries. Let's see an example:
defmodule Post do
...
def active() do
from post in Post,
where: post.active
end
end
defmodule Comment do
use Ecto.Schema
schema "comments" do
has_one :post, Post.active()
end
end
Note: building the association does not consider the query filters.
For example, if the given query requires the active field of the associated records to be true,
building such association won't automatically set the active field to true.
"""
defmacro has_one(name, queryable, opts \\ []) do
queryable = expand_alias(queryable, __CALLER__)
quote do
Ecto.Schema.__has_one__(__MODULE__, unquote(name), unquote(queryable), unquote(opts))
end
end
@doc ~S"""
Indicates a one-to-one or many-to-one association with another schema.
The current schema belongs to zero or one records of the other schema. The other
schema often has a `has_one` or a `has_many` field with the reverse association.
You should use `belongs_to` in the table that contains the foreign key. Imagine
a company <-> employee relationship. If the employee contains the `company_id` in
the underlying database table, we say the employee belongs to company.
In fact, when you invoke this macro, a field with the name of foreign key is
automatically defined in the schema for you.
## Options
* `:foreign_key` - Sets the foreign key field name, defaults to the name
of the association suffixed by `_id`. For example, `belongs_to :company`
will define foreign key of `:company_id`
* `:references` - Sets the key on the other schema to be used for the
association, defaults to: `:id`
* `:define_field` - When false, does not automatically define a `:foreign_key`
field, implying the user is defining the field manually elsewhere
* `:type` - Sets the type of automatically defined `:foreign_key`.
Defaults to: `:integer` and can be set per schema via `@foreign_key_type`
* `:on_replace` - The action taken on associations when the record is
replaced when casting or manipulating parent changeset. May be
`:raise` (default), `:mark_as_invalid`, `:nilify`, `:update`, or `:delete`.
See `Ecto.Changeset`'s section on related data for more info.
* `:defaults` - Default values to use when building the association
* `:primary_key` - If the underlying belongs_to field is a primary key
* `:source` - The source for the underlying field
* `:where` - A filter for the association. See "Filtering associations"
in `has_many/3`.
## Examples
defmodule Comment do
use Ecto.Schema
schema "comments" do
belongs_to :post, Post
end
end
# The post can come preloaded on the comment record
[comment] = Repo.all(from(c in Comment, where: c.id == 42, preload: :post))
comment.post #=> %Post{...}
If you need custom options on the underlying field, you can define the
field explicitly and then pass `define_field: false` to `belongs_to`:
defmodule Comment do
use Ecto.Schema
schema "comments" do
field :post_id, :integer, ... # custom options
belongs_to :post, Post, define_field: false
end
end
## Using Queries as Associations
A query can also be given instead of a schema. Querying, joining or preloading the association will
use the given query. Currently only where clauses can be provided in queries. Let's see an example:
defmodule Post do
...
def active() do
from post in Post,
where: post.active
end
end
defmodule Comment do
use Ecto.Schema
schema "posts" do
belongs_to :post, Post.active()
end
end
Note: building the association does not consider the query filters.
For example, if the given query requires the active field of the associated records to be true,
building such association won't automatically set the active field to true.
## Polymorphic associations
One common use case for belongs to associations is to handle
polymorphism. For example, imagine you have defined a Comment
schema and you wish to use it for commenting on both tasks and
posts.
Some abstractions would force you to define some sort of
polymorphic association with two fields in your database:
* commentable_type
* commentable_id
The problem with this approach is that it breaks references in
the database. You can't use foreign keys and it is very inefficient,
both in terms of query time and storage.
In Ecto, we have three ways to solve this issue. The simplest
is to define multiple fields in the Comment schema, one for each
association:
* task_id
* post_id
Unless you have dozens of columns, this is simpler for the developer,
more DB friendly and more efficient in all aspects.
Alternatively, because Ecto does not tie a schema to a given table,
we can use separate tables for each association. Let's start over
and define a new Comment schema:
defmodule Comment do
use Ecto.Schema
schema "abstract table: comments" do
# This will be used by associations on each "concrete" table
field :assoc_id, :integer
end
end
Notice we have changed the table name to "abstract table: comments".
You can choose whatever name you want, the point here is that this
particular table will never exist.
Now in your Post and Task schemas:
defmodule Post do
use Ecto.Schema
schema "posts" do
has_many :comments, {"posts_comments", Comment}, foreign_key: :assoc_id
end
end
defmodule Task do
use Ecto.Schema
schema "tasks" do
has_many :comments, {"tasks_comments", Comment}, foreign_key: :assoc_id
end
end
Now each association uses its own specific table, "posts_comments"
and "tasks_comments", which must be created on migrations. The
advantage of this approach is that we never store unrelated data
together, also ensuring we keep database references fast and correct.
When using this technique, the only limitation is that you cannot
build comments directly. For example, the command below
Repo.insert!(%Comment{})
will attempt to use the abstract table. Instead, one should use
Repo.insert!(build_assoc(post, :comments))
leveraging the `Ecto.build_assoc/3` function. You can also
use `Ecto.assoc/2` and `Ecto.Query.assoc/2` in the query syntax
to easily retrieve associated comments to a given post or
task:
# Fetch all comments associated with the given task
Repo.all(assoc(task, :comments))
Or all comments in a given table:
Repo.all from(c in {"posts_comments", Comment}), ...)
The third and final option is to use `many_to_many/3` to
define the relationships between the resources. In this case,
the comments table won't have the foreign key, instead there
is a intermediary table responsible for associating the entries:
defmodule Comment do
use Ecto.Schema
schema "comments" do
# ...
end
end
In your posts and tasks:
defmodule Post do
use Ecto.Schema
schema "posts" do
many_to_many :comments, Comment, join_through: "posts_comments"
end
end
defmodule Task do
use Ecto.Schema
schema "tasks" do
many_to_many :comments, Comment, join_through: "tasks_comments"
end
end
See `many_to_many/3` for more information on this particular approach.
"""
defmacro belongs_to(name, queryable, opts \\ []) do
queryable = expand_alias(queryable, __CALLER__)
quote do
Ecto.Schema.__belongs_to__(__MODULE__, unquote(name), unquote(queryable), unquote(opts))
end
end
@doc ~S"""
Indicates a many-to-many association with another schema.
The association happens through a join schema or source, containing
foreign keys to the associated schemas. For example, the association
below:
# from MyApp.Post
many_to_many :tags, MyApp.Tag, join_through: "posts_tags"
is backed by relational databases through a join table as follows:
[Post] <-> [posts_tags] <-> [Tag]
id <-- post_id
tag_id --> id
More information on the migration for creating such a schema is shown
below.
## Options
* `:join_through` - specifies the source of the associated data.
It may be a string, like "posts_tags", representing the
underlying storage table or an atom, like `MyApp.PostTag`,
representing a schema. This option is required.
* `:join_keys` - specifies how the schemas are associated. It
expects a keyword list with two entries, the first being how
the join table should reach the current schema and the second
how the join table should reach the associated schema. In the
example above, it defaults to: `[post_id: :id, tag_id: :id]`.
The keys are inflected from the schema names.
* `:on_delete` - The action taken on associations when the parent record
is deleted. May be `:nothing` (default) or `:delete_all`.
`:delete_all` will only remove data from the join source, never the
associated records. Notice `:on_delete` may also be set in migrations
when creating a reference. If your database supports it, setting the
`:on_delete` in the migration is preferred as the database can effectively
guarantee integrity, it is more efficient, and it also allows `:nilify_all`
and `:delete_all` to cascade.
* `:on_replace` - The action taken on associations when the record is
replaced when casting or manipulating parent changeset. May be
`:raise` (default), `:mark_as_invalid`, or `:delete`.
`:delete` will only remove data from the join source, never the
associated records. See `Ecto.Changeset`'s section on related data
for more info.
* `:defaults` - Default values to use when building the association
* `:unique` - When true, checks if the associated entries are unique.
This is done by checking the primary key of the associated entries during
repository operations. Keep in mind this does not guarantee uniqueness at the
database level. For such it is preferred to set a unique index in the database.
For example: `create unique_index(:posts_tags, [:post_id, :tag_id])`
* `:where` - A filter for the association. See "Filtering associations"
in `has_many/3`
* `:join_through_where` - A filter for the join through association.
See "Filtering associations" in `has_many/3`
## Removing data
If you attempt to remove associated `many_to_many` data, **Ecto will
always remove data from the join schema and never from the target
associations** be it by setting `:on_replace` to `:delete`, `:on_delete`
to `:delete_all` or by using changeset functions such as
`Ecto.Changeset.put_assoc/3`. For example, if a `Post` has a many to many
relationship with `Tag`, setting `:on_delete` to `:delete_all` will
only delete entries from the "posts_tags" table in case `Post` is
deleted.
## Migration
How your migration should be structured depends on the value you pass
in `:join_through`. If `:join_through` is simply a string, representing
a table, you may define a table without primary keys and you must not
include any further columns, as those values won't be set by Ecto:
create table(:posts_tags, primary_key: false) do
add :post_id, references(:posts)
add :tag_id, references(:tags)
end
However, if your `:join_through` is a schema, like `MyApp.PostTag`, your
join table may be structured as any other table in your codebase,
including timestamps:
create table(:posts_tags) do
add :post_id, references(:posts)
add :tag_id, references(:tags)
timestamps()
end
Because `:join_through` contains a schema, in such cases, autogenerated
values and primary keys will be automatically handled by Ecto.
## Examples
defmodule Post do
use Ecto.Schema
schema "posts" do
many_to_many :tags, Tag, join_through: "posts_tags"
end
end
# Let's create a post and a tag
post = Repo.insert!(%Post{})
tag = Repo.insert!(%Tag{name: "introduction"})
# We can associate at any time post and tags together using changesets
post
|> Repo.preload(:tags) # Load existing data
|> Ecto.Changeset.change() # Build the changeset
|> Ecto.Changeset.put_assoc(:tags, [tag]) # Set the association
|> Repo.update!
# In a later moment, we may get all tags for a given post
post = Repo.get(Post, 42)
tags = Repo.all(assoc(post, :tags))
# The tags may also be preloaded on the post struct for reading
[post] = Repo.all(from(p in Post, where: p.id == 42, preload: :tags))
post.tags #=> [%Tag{...}, ...]
## Join Schema Example
You may prefer to use a join schema to handle many_to_many associations. The
decoupled nature of Ecto allows us to create a "join" struct which
`belongs_to` both sides of the many to many association.
In our example, a User has and belongs to many Organizations
defmodule UserOrganization do
use Ecto.Schema
@primary_key false
schema "users_organizations" do
belongs_to :user, User
belongs_to :organization, Organization
timestamps() # Added bonus, a join schema will also allow you to set timestamps
end
def changeset(struct, params \\ %{}) do
struct
|> Ecto.Changeset.cast(params, [:user_id, :organization_id])
|> Ecto.Changeset.validate_required([:user_id, :organization_id])
# Maybe do some counter caching here!
end
end
defmodule User do
use Ecto.Schema
schema "users" do
many_to_many :organizations, Organization, join_through: UserOrganization
end
end
defmodule Organization do
use Ecto.Schema
schema "organizations" do
many_to_many :users, User, join_through: UserOrganization
end
end
# Then to create the association, pass in the ID's of an existing
# User and Organization to UserOrganization.changeset
changeset = UserOrganization.changeset(%UserOrganization{}, %{user_id: id, organization_id: id})
case Repo.insert(changeset) do
{:ok, assoc} -> # Assoc was created!
{:error, changeset} -> # Handle the error
end
## Using Queries as Associations
A query can also be given instead of a schema, both for the join_through and the destination.
Querying, joining or preloading the association will use the given query. Currently only where
clauses can be provided in queries. Let's see an example:
defmodule UserOrganization do
use Ecto.Schema
@primary_key false
schema "users_organizations" do
belongs_to :user, User
belongs_to :organization, Organization
field :deleted, :boolean
timestamps() # Added bonus, a join schema will also allow you to set timestamps
end
def active() do
from user_organization in UserOrganization,
where: is_nil(user_organization.deleted)
end
end
defmodule User do
use Ecto.Schema
schema "users" do
many_to_many :organizations, Organization, join_through: UserOrganization
field :banned, :boolean
end
def not_banned() do
from user in User,
where: not(user.banned)
end
end
defmodule Organization do
use Ecto.Schema
schema "organizations" do
many_to_many :users, User.not_banned(), join_through: UserOrganization.active()
end
end
Note: building the association does not consider the query filters.
For example, if the given query requires the active field of the associated records to be true,
building such association won't automatically set the active field to true.
"""
defmacro many_to_many(name, queryable, opts \\ []) do
queryable = expand_alias(queryable, __CALLER__)
quote do
Ecto.Schema.__many_to_many__(__MODULE__, unquote(name), unquote(queryable), unquote(opts))
end
end
## Embeds
@doc ~S"""
Indicates an embedding of a schema.
The current schema has zero or one records of the other schema embedded
inside of it. It uses a field similar to the `:map` type for storage,
but allows embeds to have all the things regular schema can.
You must declare your `embeds_one/3` field with type `:map` at the
database level.
The embedded may or may not have a primary key. Ecto use the primary keys
to detect if an embed is being updated or not. If a primary is not present,
`:on_replace` should be set to either `:update` or `:delete` if there is a
desire to either update or delete the current embed when a new one is set.
## Options
* `:on_replace` - The action taken on associations when the embed is
replaced when casting or manipulating parent changeset. May be
`:raise` (default), `:mark_as_invalid`, `:update`, or `:delete`.
See `Ecto.Changeset`'s section on related data for more info.
## Examples
defmodule Order do
use Ecto.Schema
schema "orders" do
embeds_one :item, Item
end
end
defmodule Item do
use Ecto.Schema
embedded_schema do
field :title
end
end
# The item is loaded with the order
order = Repo.get!(Order, 42)
order.item #=> %Item{...}
Adding and removal of embeds can only be done via the `Ecto.Changeset`
API so Ecto can properly track the embed life-cycle:
order = Repo.get!(Order, 42)
item = %Item{title: "Soap"}
# Generate a changeset
changeset = Ecto.Changeset.change(order)
# Put a new embed to the changeset
changeset = Ecto.Changeset.put_embed(changeset, :item, item)
# Update the order, and fetch the item
item = Repo.update!(changeset).item
# Item is generated with a unique identification
item
# => %Item{id: "20a97d94-f79b-4e63-a875-85deed7719b7", title: "Soap"}
## Inline embedded schema
The schema module can be defined inline in the parent schema in simple
cases:
defmodule Parent do
use Ecto.Schema
schema "parents" do
field :name, :string
embeds_one :child, Child do
field :name, :string
field :age, :integer
end
end
end
When defining an inline embed, the `:primary_key` option may be given to
customize the embed primary key type.
Options should be passed before the `do` block like this:
embeds_one :child, Child, on_replace: :delete do
field :name, :string
field :age, :integer
end
Defining embedded schema in such a way will define a `Parent.Child` module
with the appropriate struct. In order to properly cast the embedded schema.
When casting the inline-defined embedded schemas you need to use the `:with`
option of `cast_embed/3` to provide the proper function to do the casting.
For example:
def changeset(schema, params) do
schema
|> cast(params, [:name])
|> cast_embed(:child, with: &child_changeset/2)
end
defp child_changeset(schema, params) do
schema
|> cast(params, [:name, :age])
end
## Encoding and decoding
Because many databases do not support direct encoding and decoding
of embeds, it is often emulated by Ecto by using specific encoding
and decoding rules.
For example, PostgreSQL will store embeds on top of JSONB columns,
which means types in embedded schemas won't go through the usual
dump->DB->load cycle but rather encode->DB->decode->cast. This means
that, when using embedded schemas with databases like PG or MySQL,
make sure all of your types can be JSON encoded/decoded correctly.
Ecto provides this guarantee for all built-in types.
"""
defmacro embeds_one(name, schema, opts \\ [])
defmacro embeds_one(name, schema, do: block) do
quote do
embeds_one(unquote(name), unquote(schema), [], do: unquote(block))
end
end
defmacro embeds_one(name, schema, opts) do
schema = expand_alias(schema, __CALLER__)
quote do
Ecto.Schema.__embeds_one__(__MODULE__, unquote(name), unquote(schema), unquote(opts))
end
end
@doc """
Indicates an embedding of a schema.
For options and examples see documentation of `embeds_one/3`.
"""
defmacro embeds_one(name, schema, opts, do: block) do
quote do
{schema, opts} = Ecto.Schema.__embeds_module__(__ENV__, unquote(schema), unquote(opts), unquote(Macro.escape(block)))
Ecto.Schema.__embeds_one__(__MODULE__, unquote(name), schema, opts)
end
end
@doc ~S"""
Indicates an embedding of many schemas.
The current schema has zero or more records of the other schema embedded
inside of it. Embeds have all the things regular schemas have.
It is recommended to declare your `embeds_many/3` field with type `:map`
and a default of `"[]"` (although Ecto will also automatically translate
`nil` values from the database into empty lists).
The embedded may or may not have a primary key. Ecto use the primary keys
to detect if an embed is being updated or not. If a primary is not present
and you still want the list of embeds to be updated, `:on_replace` must be
set to `:delete`, forcing all current embeds to be deleted and replaced by
new ones whenever a new list of embeds is set.
For encoding and decoding of embeds, please read the docs for
`embeds_one/3`.
## Options
* `:on_replace` - The action taken on associations when the embed is
replaced when casting or manipulating parent changeset. May be
`:raise` (default), `:mark_as_invalid`, or `:delete`.
See `Ecto.Changeset`'s section on related data for more info.
## Examples
defmodule Order do
use Ecto.Schema
schema "orders" do
embeds_many :items, Item
end
end
defmodule Item do
use Ecto.Schema
embedded_schema do
field :title
end
end
# The items are loaded with the order
order = Repo.get!(Order, 42)
order.items #=> [%Item{...}, ...]
Adding and removal of embeds can only be done via the `Ecto.Changeset`
API so Ecto can properly track the embed life-cycle:
# Order has no items
order = Repo.get!(Order, 42)
order.items
# => []
items = [%Item{title: "Soap"}]
# Generate a changeset
changeset = Ecto.Changeset.change(order)
# Put a one or more new items
changeset = Ecto.Changeset.put_embed(changeset, :items, items)
# Update the order and fetch items
items = Repo.update!(changeset).items
# Items are generated with a unique identification
items
# => [%Item{id: "20a97d94-f79b-4e63-a875-85deed7719b7", title: "Soap"}]
Updating of embeds must be done using a changeset for each changed embed.
# Order has an existing items
order = Repo.get!(Order, 42)
order.items
# => [%Item{id: "20a97d94-f79b-4e63-a875-85deed7719b7", title: "Soap"}]
# Generate a changeset
changeset = Ecto.Changeset.change(order)
# Put the updated item as a changeset
current_item = List.first(order.items)
item_changeset = Ecto.Changeset.change(current_item, title: "Mujju's Soap")
order_changeset = Ecto.Changeset.put_embed(changeset, :items, [item_changeset])
# Update the order and fetch items
items = Repo.update!(order_changeset).items
# Item has the updated title
items
# => [%Item{id: "20a97d94-f79b-4e63-a875-85deed7719b7", title: "Mujju's Soap"}]
## Inline embedded schema
The schema module can be defined inline in the parent schema in simple
cases:
defmodule Parent do
use Ecto.Schema
schema "parents" do
field :name, :string
embeds_many :children, Child do
field :name, :string
field :age, :integer
end
end
end
When defining an inline embed, the `:primary_key` option may be given to
customize the embed primary key type.
Defining embedded schema in such a way will define a `Parent.Child` module
with the appropriate struct. In order to properly cast the embedded schema.
When casting the inline-defined embedded schemas you need to use the `:with`
option of `cast_embed/3` to provide the proper function to do the casting.
For example:
def changeset(schema, params) do
schema
|> cast(params, [:name])
|> cast_embed(:children, with: &child_changeset/2)
end
defp child_changeset(schema, params) do
schema
|> cast(params, [:name, :age])
end
"""
defmacro embeds_many(name, schema, opts \\ [])
defmacro embeds_many(name, schema, do: block) do
quote do
embeds_many(unquote(name), unquote(schema), [], do: unquote(block))
end
end
defmacro embeds_many(name, schema, opts) do
schema = expand_alias(schema, __CALLER__)
quote do
Ecto.Schema.__embeds_many__(__MODULE__, unquote(name), unquote(schema), unquote(opts))
end
end
@doc """
Indicates an embedding of many schemas.
For options and examples see documentation of `embeds_many/3`.
"""
defmacro embeds_many(name, schema, opts, do: block) do
quote do
{schema, opts} = Ecto.Schema.__embeds_module__(__ENV__, unquote(schema), unquote(opts), unquote(Macro.escape(block)))
Ecto.Schema.__embeds_many__(__MODULE__, unquote(name), schema, opts)
end
end
@doc """
Internal function for integrating associations into schemas.
This function exists as an extension point for libraries to
add new types of associations to Ecto. For the existing APIs,
see `belongs_to/3`, `has_many/3`, `has_one/3` and `many_to_many/3`.
This function expects the current schema, the association cardinality,
the association name, the association module (that implements
`Ecto.Association` callbacks) and a keyword list of options.
"""
@spec association(module, :one | :many, atom(), module, Keyword.t) :: Ecto.Association.t
def association(schema, cardinality, name, association, opts) do
not_loaded = %Ecto.Association.NotLoaded{
__owner__: schema,
__field__: name,
__cardinality__: cardinality
}
put_struct_field(schema, name, not_loaded)
opts = [cardinality: cardinality] ++ opts
struct = association.struct(schema, name, opts)
Module.put_attribute(schema, :ecto_assocs, {name, struct})
struct
end
## Callbacks
@doc false
def __timestamps__(:naive_datetime) do
%{NaiveDateTime.utc_now() | microsecond: {0, 0}}
end
def __timestamps__(:naive_datetime_usec) do
NaiveDateTime.utc_now()
end
def __timestamps__(:utc_datetime) do
DateTime.from_unix!(System.system_time(:second), :second)
end
def __timestamps__(:utc_datetime_usec) do
DateTime.from_unix!(System.system_time(:microsecond), :microsecond)
end
def __timestamps__(type) do
type.from_unix!(System.system_time(:microsecond), :microsecond)
end
@doc false
# Loads data into struct by assumes fields are properly
# named and belongs to the struct. Types and values are
# zipped together in one pass as they are loaded.
def __safe_load__(struct, types, values, prefix, source, loader) do
zipped = safe_load_zip(types, values, struct, loader)
case Map.merge(struct, Map.new(zipped)) do
%{__meta__: %Metadata{} = metadata} = struct ->
metadata = %{metadata | state: :loaded, source: source, prefix: prefix}
Map.put(struct, :__meta__, metadata)
map ->
map
end
end
defp safe_load_zip([{field, type} | fields], [value | values], struct, loader) do
[{field, load!(struct, field, type, value, loader)} |
safe_load_zip(fields, values, struct, loader)]
end
defp safe_load_zip([], [], _struct, _loader) do
[]
end
@doc false
# Assumes data does not all belongs to schema/struct
# and that it may also require source-based renaming.
def __unsafe_load__(schema, data, loader) do
types = schema.__schema__(:load)
struct = schema.__struct__()
case __unsafe_load__(struct, types, data, loader) do
%{__meta__: %Metadata{} = metadata} = struct ->
Map.put(struct, :__meta__, %{metadata | state: :loaded})
map ->
map
end
end
@doc false
def __unsafe_load__(struct, types, map, loader) when is_map(map) do
Enum.reduce(types, struct, fn pair, acc ->
{field, source, type} = field_source_and_type(pair)
case fetch_string_or_atom_field(map, source) do
{:ok, value} -> Map.put(acc, field, load!(struct, field, type, value, loader))
:error -> acc
end
end)
end
@compile {:inline, field_source_and_type: 1, fetch_string_or_atom_field: 2}
defp field_source_and_type({field, {:source, source, type}}) do
{field, source, type}
end
defp field_source_and_type({field, type}) do
{field, field, type}
end
defp fetch_string_or_atom_field(map, field) when is_atom(field) do
case Map.fetch(map, Atom.to_string(field)) do
{:ok, value} -> {:ok, value}
:error -> Map.fetch(map, field)
end
end
defp load!(struct, field, type, value, loader) do
case loader.(type, value) do
{:ok, value} ->
value
:error ->
raise ArgumentError, "cannot load `#{inspect value}` as type #{inspect type} " <>
"for field `#{field}`#{error_data(struct)}"
end
end
defp error_data(%{__struct__: atom}) do
" in schema #{inspect atom}"
end
defp error_data(other) when is_map(other) do
""
end
@doc false
def __field__(mod, name, type, opts) do
check_field_type!(name, type, opts)
define_field(mod, name, type, opts)
end
defp define_field(mod, name, type, opts) do
virtual? = opts[:virtual] || false
pk? = opts[:primary_key] || false
Module.put_attribute(mod, :changeset_fields, {name, type})
put_struct_field(mod, name, Keyword.get(opts, :default))
unless virtual? do
source = opts[:source] || Module.get_attribute(mod, :field_source_mapper).(name)
if name != source do
Module.put_attribute(mod, :ecto_field_sources, {name, source})
end
if raw = opts[:read_after_writes] do
Module.put_attribute(mod, :ecto_raw, name)
end
case gen = opts[:autogenerate] do
{_, _, _} ->
store_mfa_autogenerate!(mod, name, type, gen)
true ->
store_type_autogenerate!(mod, name, source || name, type, pk?)
_ ->
:ok
end
if raw && gen do
raise ArgumentError, "cannot mark the same field as autogenerate and read_after_writes"
end
if pk? do
Module.put_attribute(mod, :ecto_primary_keys, name)
end
Module.put_attribute(mod, :ecto_fields, {name, type})
end
end
@valid_has_options [:foreign_key, :references, :through, :on_delete, :defaults, :on_replace, :where]
@doc false
def __has_many__(mod, name, queryable, opts) do
check_options!(opts, @valid_has_options, "has_many/3")
if is_list(queryable) and Keyword.has_key?(queryable, :through) do
association(mod, :many, name, Ecto.Association.HasThrough, queryable)
else
struct =
association(mod, :many, name, Ecto.Association.Has, [queryable: queryable] ++ opts)
Module.put_attribute(mod, :changeset_fields, {name, {:assoc, struct}})
end
end
@doc false
def __has_one__(mod, name, queryable, opts) do
check_options!(opts, @valid_has_options, "has_one/3")
if is_list(queryable) and Keyword.has_key?(queryable, :through) do
association(mod, :one, name, Ecto.Association.HasThrough, queryable)
else
struct =
association(mod, :one, name, Ecto.Association.Has, [queryable: queryable] ++ opts)
Module.put_attribute(mod, :changeset_fields, {name, {:assoc, struct}})
end
end
# :primary_key is valid here to support associative entity
# https://en.wikipedia.org/wiki/Associative_entity
@valid_belongs_to_options [:foreign_key, :references, :define_field, :type,
:on_replace, :defaults, :primary_key, :source, :where]
@doc false
def __belongs_to__(mod, name, queryable, opts) do
check_options!(opts, @valid_belongs_to_options, "belongs_to/3")
opts = Keyword.put_new(opts, :foreign_key, :"#{name}_id")
foreign_key_type = opts[:type] || Module.get_attribute(mod, :foreign_key_type)
if name == Keyword.get(opts, :foreign_key) do
raise ArgumentError, "foreign_key #{inspect name} must be distinct from corresponding association name"
end
if Keyword.get(opts, :define_field, true) do
__field__(mod, opts[:foreign_key], foreign_key_type, opts)
end
struct =
association(mod, :one, name, Ecto.Association.BelongsTo, [queryable: queryable] ++ opts)
Module.put_attribute(mod, :changeset_fields, {name, {:assoc, struct}})
end
@valid_many_to_many_options [:join_through, :join_keys, :on_delete, :defaults, :on_replace,
:unique, :where, :join_through_where]
@doc false
def __many_to_many__(mod, name, queryable, opts) do
check_options!(opts, @valid_many_to_many_options, "many_to_many/3")
struct =
association(mod, :many, name, Ecto.Association.ManyToMany, [queryable: queryable] ++ opts)
Module.put_attribute(mod, :changeset_fields, {name, {:assoc, struct}})
end
@valid_embeds_one_options [:strategy, :on_replace, :source]
@doc false
def __embeds_one__(mod, name, schema, opts) do
check_options!(opts, @valid_embeds_one_options, "embeds_one/3")
embed(mod, :one, name, schema, opts)
end
@valid_embeds_many_options [:strategy, :on_replace, :source]
@doc false
def __embeds_many__(mod, name, schema, opts) do
check_options!(opts, @valid_embeds_many_options, "embeds_many/3")
opts = Keyword.put(opts, :default, [])
embed(mod, :many, name, schema, opts)
end
@doc false
def __embeds_module__(env, name, opts, block) do
{pk, opts} = Keyword.pop(opts, :primary_key, {:id, :binary_id, autogenerate: true})
block =
quote do
use Ecto.Schema
@primary_key unquote(Macro.escape(pk))
embedded_schema do
unquote(block)
end
end
module = Module.concat(env.module, name)
Module.create(module, block, env)
{module, opts}
end
## Quoted callbacks
@doc false
def __after_compile__(%{module: module} = env, _) do
# If we are compiling code, we can validate associations now,
# as the Elixir compiler will solve dependencies.
#
# TODO: This is a hack, don't do this at home, it may break any time.
# Instead Elixir should provide a proper API to check for compilation.
if Process.info(self(), :error_handler) == {:error_handler, Kernel.ErrorHandler} do
for name <- module.__schema__(:associations) do
assoc = module.__schema__(:association, name)
case assoc.__struct__.after_compile_validation(assoc, env) do
:ok ->
:ok
{:error, message} ->
IO.warn "invalid association `#{assoc.field}` in schema #{inspect module}: #{message}",
Macro.Env.stacktrace(env)
end
end
end
:ok
end
@doc false
def __schema__(fields, field_sources, assocs, embeds) do
load =
for {name, type} <- fields do
if alias = field_sources[name] do
{name, {:source, alias, type}}
else
{name, type}
end
end
dump =
for {name, type} <- fields do
{name, {field_sources[name] || name, type}}
end
field_sources_quoted =
for {name, _type} <- fields do
{[:field_source, name], field_sources[name] || name}
end
types_quoted =
for {name, type} <- fields do
{[:type, name], Macro.escape(type)}
end
assoc_quoted =
for {name, refl} <- assocs do
{[:association, name], Macro.escape(refl)}
end
assoc_names = Enum.map(assocs, &elem(&1, 0))
embed_quoted =
for {name, refl} <- embeds do
{[:embed, name], Macro.escape(refl)}
end
embed_names = Enum.map(embeds, &elem(&1, 0))
single_arg = [
{[:dump], dump |> Map.new() |> Macro.escape()},
{[:load], load |> Macro.escape()},
{[:associations], assoc_names},
{[:embeds], embed_names}
]
catch_all = [
{[:field_source, quote(do: _)], nil},
{[:type, quote(do: _)], nil},
{[:association, quote(do: _)], nil},
{[:embed, quote(do: _)], nil}
]
[
single_arg,
field_sources_quoted,
types_quoted,
assoc_quoted,
embed_quoted,
catch_all
]
end
## Private
defp embed(mod, cardinality, name, schema, opts) do
opts = [cardinality: cardinality, related: schema] ++ opts
struct = Ecto.Embedded.struct(mod, name, opts)
define_field(mod, name, {:embed, struct}, opts)
Module.put_attribute(mod, :ecto_embeds, {name, struct})
end
defp put_struct_field(mod, name, assoc) do
fields = Module.get_attribute(mod, :struct_fields)
if List.keyfind(fields, name, 0) do
raise ArgumentError, "field/association #{inspect name} is already set on schema"
end
Module.put_attribute(mod, :struct_fields, {name, assoc})
end
defp check_options!(opts, valid, fun_arity) do
case Enum.find(opts, fn {k, _} -> not(k in valid) end) do
{k, _} -> raise ArgumentError, "invalid option #{inspect k} for #{fun_arity}"
nil -> :ok
end
end
defp check_field_type!(name, :datetime, _opts) do
raise ArgumentError, "invalid type :datetime for field #{inspect name}. " <>
"You probably meant to choose one between :naive_datetime " <>
"(no time zone information) or :utc_datetime (time zone is set to UTC)"
end
defp check_field_type!(name, {:embed, _}, _opts) do
raise ArgumentError, "cannot declare field #{inspect name} as embed. Use embeds_one/many instead"
end
defp check_field_type!(name, type, opts) do
cond do
type == :any and !opts[:virtual] ->
raise ArgumentError, "only virtual fields can have type :any, " <>
"invalid type for field #{inspect name}"
Ecto.Type.primitive?(type) ->
type
is_atom(type) and Code.ensure_compiled?(type) and function_exported?(type, :type, 0) ->
type
is_atom(type) and function_exported?(type, :__schema__, 1) ->
raise ArgumentError,
"schema #{inspect type} is not a valid type for field #{inspect name}." <>
" Did you mean to use belongs_to, has_one, has_many, embeds_one, or embeds_many instead?"
true ->
raise ArgumentError, "invalid or unknown type #{inspect type} for field #{inspect name}"
end
end
defp store_mfa_autogenerate!(mod, name, type, mfa) do
if autogenerate_id(type) do
raise ArgumentError, ":autogenerate with {m, f, a} not supported by ID types"
else
Module.put_attribute(mod, :ecto_autogenerate, {name, mfa})
end
end
defp store_type_autogenerate!(mod, name, source, type, pk?) do
cond do
id = autogenerate_id(type) ->
cond do
not pk? ->
raise ArgumentError, "only primary keys allow :autogenerate for type #{inspect type}, " <>
"field #{inspect name} is not a primary key"
Module.get_attribute(mod, :ecto_autogenerate_id) ->
raise ArgumentError, "only one primary key with ID type may be marked as autogenerated"
true ->
Module.put_attribute(mod, :ecto_autogenerate_id, {name, source, id})
end
Ecto.Type.primitive?(type) ->
raise ArgumentError, "field #{inspect name} does not support :autogenerate because it uses a " <>
"primitive type #{inspect type}"
# Note the custom type has already been loaded in check_type!/3
not function_exported?(type, :autogenerate, 0) ->
raise ArgumentError, "field #{inspect name} does not support :autogenerate because it uses a " <>
"custom type #{inspect type} that does not define autogenerate/0"
true ->
Module.put_attribute(mod, :ecto_autogenerate, {name, {type, :autogenerate, []}})
end
end
defp autogenerate_id(type) do
id = if Ecto.Type.primitive?(type), do: type, else: type.type
if id in [:id, :binary_id], do: id, else: nil
end
defp expand_alias({:__aliases__, _, _} = ast, env),
do: Macro.expand(ast, %{env | function: {:__schema__, 2}})
defp expand_alias(ast, _env),
do: ast
end