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type.ex
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defmodule Ecto.Type do
@moduledoc """
Defines functions and the `Ecto.Type` behaviour for implementing
custom types.
A custom type expects 4 functions to be implemented, all documented
and described below. We also provide two examples of how custom
types can be used in Ecto to augment existing types or providing
your own types.
## Augmenting types
Imagine you want to support your id field to be looked up as a
permalink. For example, you want the following query to work:
permalink = "10-how-to-be-productive-with-elixir"
from p in Post, where: p.id == ^permalink
If `id` is an integer field, Ecto will fail in the query above
because it cannot cast the string to an integer. By using a
custom type, we can provide special casting behaviour while
still keeping the underlying Ecto type the same:
defmodule Permalink do
def type, do: :integer
# Provide our own casting rules.
def cast(string) when is_binary(string) do
case Integer.parse(string) do
{int, _} -> {:ok, int}
:error -> :error
end
end
# We should still accept integers
def cast(integer) when is_integer(integer), do: {:ok, integer}
# Everything else is a failure though
def cast(_), do: :error
# When loading data from the database, we are guaranteed to
# receive an integer (as database are stricts) and we will
# just return it to be stored in the model struct.
def load(integer) when is_integer(integer), do: {:ok, integer}
# When dumping data to the database, we *expect* an integer
# but any value could be inserted into the struct, so we need
# guard against them.
def dump(integer) when is_integer(integer), do: {:ok, integer}
def dump(_), do: :error
end
Now, we can use our new field above as our primary key type in models:
defmodule Post do
use Ecto.Model
@primary_key {:id, Permalink, autogenerate: true}
schema "posts" do
...
end
end
## New types
In the previous example, we say we were augmenting an existing type
because we were keeping the underlying representation the same, the
value stored in the struct and the database was always an integer.
However, sometimes, we want to completely replace Ecto data types
stored in the models. This is for example how Ecto provides the
`Ecto.DateTime` struct as a replacement for the `:datetime` type.
Check the `Ecto.DateTime` implementation for an example on how
to implement such types.
"""
import Kernel, except: [match?: 2]
use Behaviour
@type t :: primitive | custom
@type primitive :: base | composite
@type custom :: atom
@typep base :: :integer | :float | :boolean | :string |
:binary | :decimal | :datetime | :time |
:date | :id | :binary_id | :map | :any
@typep composite :: {:array, base}
@base ~w(integer float boolean string binary decimal datetime time date id binary_id map any)a
@composite ~w(array)a
@doc """
Returns the underlying schema type for the custom type.
For example, if you want to provide your own datetime
structures, the type function should return `:datetime`.
"""
defcallback type :: base | custom
@doc """
Casts the given input to the custom type.
This callback is called on external input and can return any type,
as long as the `dump/1` function is able to convert the returned
value back into an Ecto native type. There are two situations where
this callback is called:
1. When casting values by `Ecto.Changeset`
2. When passing arguments to `Ecto.Query`
"""
defcallback cast(term) :: {:ok, term} | :error
@doc """
Loads the given term into a custom type.
This callback is called when loading data from the database and
receive an Ecto native type. It can return any type, as long as
the `dump/1` function is able to convert the returned value back
into an Ecto native type.
"""
defcallback load(term) :: {:ok, term} | :error
@doc """
Dumps the given term into an Ecto native type.
This callback is called with any term that was stored in the struct
and it needs to validate them and convert it to an Ecto native type.
"""
defcallback dump(term) :: {:ok, term} | :error
## Functions
@doc """
Checks if we have a primitive type.
iex> primitive?(:string)
true
iex> primitive?(Another)
false
iex> primitive?({:array, :string})
true
iex> primitive?({:array, Another})
true
"""
@spec primitive?(t) :: boolean
def primitive?({composite, _}) when composite in @composite, do: true
def primitive?(base) when base in @base, do: true
def primitive?(_), do: false
@doc """
Checks if the given atom can be used as composite type.
iex> composite?(:array)
true
iex> composite?(:string)
false
"""
@spec composite?(atom) :: boolean
def composite?(atom), do: atom in @composite
@doc """
Checks if the given atom can be used as base type.
iex> base?(:string)
true
iex> base?(:array)
false
iex> base?(Custom)
false
"""
@spec base?(atom) :: boolean
def base?(atom), do: atom in @base
@doc """
Retrieves the underlying type of a given type.
iex> type(:string)
:string
iex> type(Ecto.DateTime)
:datetime
iex> type({:array, :string})
{:array, :string}
iex> type({:array, Ecto.DateTime})
{:array, :datetime}
"""
@spec type(t) :: t
def type(type)
def type({:array, type}), do: {:array, type(type)}
def type(type) do
if primitive?(type) do
type
else
type.type
end
end
@doc """
Normalizes a type.
The only type normalizable is binary_id which comes
from the adapter.
"""
def normalize({comp, :binary_id}, %{binary_id: binary_id}), do: {comp, binary_id}
def normalize(:binary_id, %{binary_id: binary_id}), do: binary_id
def normalize(:binary_id, %{}), do: raise "adapter did not provide a type for :binary_id"
def normalize(type, _id_types), do: type
@doc """
Checks if a given type matches with a primitive type
that can be found in queries.
iex> match?(:whatever, :any)
true
iex> match?(:any, :whatever)
true
iex> match?(:string, :string)
true
iex> match?({:array, :string}, {:array, :any})
true
iex> match?(Ecto.DateTime, :datetime)
true
iex> match?(Ecto.DateTime, :string)
false
"""
@spec match?(t, primitive) :: boolean
def match?(schema_type, query_type)
def match?(_left, :any), do: true
def match?(:any, _right), do: true
def match?(type, primitive) do
if primitive?(type) do
do_match?(type, primitive)
else
do_match?(type.type, primitive)
end
end
defp do_match?({outer, left}, {outer, right}), do: match?(left, right)
defp do_match?(:decimal, type) when type in [:float, :integer], do: true
defp do_match?(:binary_id, :binary), do: true
defp do_match?(:id, :integer), do: true
defp do_match?(type, type), do: true
defp do_match?(_, _), do: false
@doc """
Dumps a value to the given type.
Opposite to casting, dumping requires the returned value
to be a valid Ecto type, as it will be sent to the
underlying data store.
iex> dump(:string, nil)
{:ok, %Ecto.Query.Tagged{value: nil, type: :string}}
iex> dump(:string, "foo")
{:ok, "foo"}
iex> dump(:integer, 1)
{:ok, 1}
iex> dump(:integer, "10")
:error
iex> dump(:binary, "foo")
{:ok, %Ecto.Query.Tagged{value: "foo", type: :binary}}
iex> dump(:binary, 1)
:error
iex> dump({:array, :integer}, [1, 2, 3])
{:ok, [1, 2, 3]}
iex> dump({:array, :integer}, [1, "2", 3])
:error
iex> dump({:array, :binary}, ["1", "2", "3"])
{:ok, %Ecto.Query.Tagged{value: ["1", "2", "3"], type: {:array, :binary}}}
"""
@spec dump(t, term) :: {:ok, term} | :error
def dump(type, nil) do
{:ok, %Ecto.Query.Tagged{value: nil, type: type(type)}}
end
def dump({:array, type}, value) do
dump_array(type, value, [], false)
end
def dump(type, value) do
cond do
not primitive?(type) ->
type.dump(value)
of_base_type?(type, value) ->
{:ok, tag(type, value)}
true ->
:error
end
end
defp tag(:binary, value),
do: %Ecto.Query.Tagged{type: :binary, value: value}
defp tag(_type, value),
do: value
defp dump_array(type, [h|t], acc, tagged) do
case dump(type, h) do
{:ok, %Ecto.Query.Tagged{value: h}} ->
dump_array(type, t, [h|acc], true)
{:ok, h} ->
dump_array(type, t, [h|acc], tagged)
:error ->
:error
end
end
defp dump_array(type, [], acc, true) do
{:ok, %Ecto.Query.Tagged{value: Enum.reverse(acc), type: {:array, type(type)}}}
end
defp dump_array(_type, [], acc, false) do
{:ok, Enum.reverse(acc)}
end
@doc """
Same as `dump/2` but raises if value can't be dumped.
"""
@spec dump!(t, term) :: term | no_return
def dump!(type, term) do
case dump(type, term) do
{:ok, value} -> value
:error -> raise ArgumentError, "cannot dump `#{inspect term}` to type #{inspect type}"
end
end
@doc """
Loads a value with the given type.
Load is invoked when loading database native types
into a struct.
iex> load(:string, nil)
{:ok, nil}
iex> load(:string, "foo")
{:ok, "foo"}
iex> load(:integer, 1)
{:ok, 1}
iex> load(:integer, "10")
:error
"""
@spec load(t, term) :: {:ok, term} | :error
def load(_type, nil), do: {:ok, nil}
def load(:boolean, 0), do: {:ok, false}
def load(:boolean, 1), do: {:ok, true}
def load(:map, value) when is_binary(value) do
{:ok, Application.get_env(:ecto, :json_library).decode!(value)}
end
def load({:array, type}, value) do
array(type, value, &load/2, [])
end
def load(type, value) do
cond do
not primitive?(type) ->
type.load(value)
of_base_type?(type, value) ->
{:ok, value}
true ->
:error
end
end
@doc """
Same as `load/2` but raises if value can't be loaded.
"""
@spec load!(t, term) :: term | no_return
def load!(type, term) do
case load(type, term) do
{:ok, value} -> value
:error -> raise ArgumentError, "cannot load `#{inspect term}` as type #{inspect type}"
end
end
@doc """
Casts a value to the given type.
`cast/2` is used by the finder queries and changesets
to cast outside values to specific types.
Note that nil can be cast to all primitive types as data
stores allow nil to be set on any column. Custom data types
may want to handle nil specially though.
iex> cast(:any, "whatever")
{:ok, "whatever"}
iex> cast(:any, nil)
{:ok, nil}
iex> cast(:string, nil)
{:ok, nil}
iex> cast(:integer, 1)
{:ok, 1}
iex> cast(:integer, "1")
{:ok, 1}
iex> cast(:integer, "1.0")
:error
iex> cast(:id, 1)
{:ok, 1}
iex> cast(:id, "1")
{:ok, 1}
iex> cast(:id, "1.0")
:error
iex> cast(:float, 1.0)
{:ok, 1.0}
iex> cast(:float, 1)
{:ok, 1.0}
iex> cast(:float, "1")
{:ok, 1.0}
iex> cast(:float, "1.0")
{:ok, 1.0}
iex> cast(:float, "1-foo")
:error
iex> cast(:boolean, true)
{:ok, true}
iex> cast(:boolean, false)
{:ok, false}
iex> cast(:boolean, "1")
{:ok, true}
iex> cast(:boolean, "0")
{:ok, false}
iex> cast(:boolean, "whatever")
:error
iex> cast(:string, "beef")
{:ok, "beef"}
iex> cast(:binary, "beef")
{:ok, "beef"}
iex> cast(:decimal, Decimal.new(1.0))
{:ok, Decimal.new(1.0)}
iex> cast(:decimal, Decimal.new("1.0"))
{:ok, Decimal.new(1.0)}
iex> cast({:array, :integer}, [1, 2, 3])
{:ok, [1, 2, 3]}
iex> cast({:array, :integer}, ["1", "2", "3"])
{:ok, [1, 2, 3]}
iex> cast({:array, :string}, [1, 2, 3])
:error
iex> cast(:string, [1, 2, 3])
:error
"""
@spec cast(t, term) :: {:ok, term} | :error
def cast(_type, nil), do: {:ok, nil}
def cast({:array, type}, term) when is_list(term) do
array(type, term, &cast/2, [])
end
def cast(:float, term) when is_binary(term) do
case Float.parse(term) do
{float, ""} -> {:ok, float}
_ -> :error
end
end
def cast(:float, term) when is_integer(term), do: {:ok, term + 0.0}
def cast(:boolean, term) when term in ~w(true 1), do: {:ok, true}
def cast(:boolean, term) when term in ~w(false 0), do: {:ok, false}
def cast(:decimal, term) when is_binary(term) or is_number(term) do
{:ok, Decimal.new(term)} # TODO: Add Decimal.parse/1
rescue
Decimal.Error -> :error
end
def cast(type, term) when type in [:id, :integer] and is_binary(term) do
case Integer.parse(term) do
{int, ""} -> {:ok, int}
_ -> :error
end
end
def cast(type, value) do
cond do
not primitive?(type) ->
type.cast(value)
of_base_type?(type, value) ->
{:ok, value}
true ->
:error
end
end
@doc """
Same as `cast/2` but raises if value can't be cast.
"""
@spec cast!(t, term) :: term | no_return
def cast!(type, term) do
case cast(type, term) do
{:ok, value} -> value
:error -> raise ArgumentError, "cannot cast `#{inspect term}` to type #{inspect type}"
end
end
## Helpers
# Checks if a value is of the given primitive type.
defp of_base_type?(:any, _), do: true
defp of_base_type?(:id, term), do: is_integer(term)
defp of_base_type?(:float, term), do: is_float(term)
defp of_base_type?(:integer, term), do: is_integer(term)
defp of_base_type?(:boolean, term), do: is_boolean(term)
defp of_base_type?(:binary, term), do: is_binary(term)
defp of_base_type?(:string, term), do: is_binary(term)
defp of_base_type?(:map, term), do: is_map(term) and not Map.has_key?(term, :__struct__)
defp of_base_type?(:decimal, %Decimal{}), do: true
defp of_base_type?(:date, {_, _, _}), do: true
defp of_base_type?(:time, {_, _, _}), do: true
defp of_base_type?(:time, {_, _, _, _}), do: true
defp of_base_type?(:datetime, {{_, _, _}, {_, _, _}}), do: true
defp of_base_type?(:datetime, {{_, _, _}, {_, _, _, _}}), do: true
defp of_base_type?(:binary_id, value) do
raise "cannot dump/cast/load :binary_id type, attempted value: #{inspect value}"
end
defp of_base_type?(:date, %{__struct__: Ecto.Date} = d) do
raise "trying to dump/cast Ecto.Date as a :date type: #{inspect d}. " <>
"Maybe you wanted to declare Ecto.Date in your schema?"
end
defp of_base_type?(:time, %{__struct__: Ecto.Time} = t) do
raise "trying to dump/cast Ecto.Time as a :time type: #{inspect t}. " <>
"Maybe you wanted to declare Ecto.Time in your schema?"
end
defp of_base_type?(:datetime, %{__struct__: Ecto.DateTime} = dt) do
raise "trying to dump/cast Ecto.DateTime as a :datetime type: #{inspect dt}. " <>
"Maybe you wanted to declare Ecto.DateTime in your schema?"
end
defp of_base_type?(struct, _) when struct in ~w(decimal date time datetime)a, do: false
defp array(type, [h|t], fun, acc) do
case fun.(type, h) do
{:ok, h} -> array(type, t, fun, [h|acc])
:error -> :error
end
end
defp array(_type, [], _fun, acc) do
{:ok, Enum.reverse(acc)}
end
end