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Fix typos and make examples more explicit
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bkoltai committed Jul 21, 2016
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139 changes: 77 additions & 62 deletions docs/howto/upgrade_from_0_8_to_0_10.md
Expand Up @@ -5,7 +5,7 @@
## Disclaimer
### Proceed at your own risk
This document attempts to outline steps to upgrade your app based on the collective experience of
developers who have done this already. It may not cover all edge cases and situation that may cause issues,
developers who have done this already. It may not cover all edge cases and situations that may cause issues,
so please proceed with a certain level of caution.

## Overview
Expand All @@ -15,30 +15,46 @@ the migration successfully. The method has been tested specifically for migratin
to `0.10.2`.

The high level approach is to upgrade to `0.10` and change all serializers to use
a backwards-compatible `VersionEightSerializer`or `VersionEightCollectionSerializer`
and a `VersionEightAdapter`. After a few more manual changes, you should have the same
a backwards-compatible `ActiveModel::V08::Serializer`or `ActiveModel::V08::CollectionSerializer`
and a `ActiveModelSerializers::Adapter::V08Adapter`. After a few more manual changes, you should have the same
functionality as you had with `AMS 0.8`. Then, you can continue to develop in your app by creating
new serializers that don't use these backwards compatible versions and slowly migrate
existing serializers to the `0.10` versions as needed.

### `0.10` breaking changes
- Passing a serializer to `render json:` is no longer supported
- Ex. `render json: CustomerSerializer.new(customer)`

```ruby
render json: CustomerSerializer.new(customer) # rendered in 0.8, errors in 0.10
```
- Passing a nil resource to serializer now fails
- Ex. `CustomerSerializer.new(nil)`
- Attribute methods are no longer accessible from other serializer methods
- Ex.
```ruby
class MySerializer
attributes :foo, :bar

def foo
bar + 1
end
end
```

```ruby
CustomerSerializer.new(nil) # returned nil in 0.8, throws error in 0.10
```
- Attribute methods are no longer defined on the serializer, and must be explicitly
accessed through `object`

```ruby
class MySerializer
attributes :foo, :bar

def foo
bar + 1 # bar does not work, needs to be object.bar in 0.10
end
end
```
- `root` option to collection serializer behaves differently
- Ex. `ActiveModel::ArraySerializer.new(resources, root: "resources")`

```ruby
# in 0.8
ActiveModel::ArraySerializer.new(resources, root: "resources")
# resulted in { "resources": <serialized_resources> }, does not work in 0.10
```
- No default serializer when serializer doesn't exist
- `@options` changed to `instance_options`

Expand All @@ -47,41 +63,42 @@ existing serializers to the `0.10` versions as needed.
### 1. Upgrade the `active_model_serializer` gem in you `Gemfile`
Change to `gem 'active_model_serializers', '~> 0.10'` and run `bundle install`

### 2. Add `VersionEightSerializer`
### 2. Add `ActiveModel::V08::Serializer`

#### Code
```ruby
module ActiveModel
class VersionEightSerializer < Serializer
include Rails.application.routes.url_helpers

# AMS 0.8 would delegate method calls from within the serializer to the
# object.
def method_missing(*args)
method = args.first
read_attribute_for_serialization(method)
end

alias_method :options, :instance_options

# Since attributes could be read from the `object` via `method_missing`,
# the `try` method did not behave as before. This patches `try` with the
# original implementation plus the addition of
# ` || object.respond_to?(a.first, true)` to check if the object responded to
# the given method.
def try(*a, &b)
if a.empty? || respond_to?(a.first, true) || object.respond_to?(a.first, true)
try!(*a, &b)
module V08
class Serializer < ActiveModel::Serializer
include Rails.application.routes.url_helpers

# AMS 0.8 would delegate method calls from within the serializer to the
# object.
def method_missing(*args)
method = args.first
read_attribute_for_serialization(method)
end

alias_method :options, :instance_options

# Since attributes could be read from the `object` via `method_missing`,
# the `try` method did not behave as before. This patches `try` with the
# original implementation plus the addition of
# ` || object.respond_to?(a.first, true)` to check if the object responded to
# the given method.
def try(*a, &b)
if a.empty? || respond_to?(a.first, true) || object.respond_to?(a.first, true)
try!(*a, &b)
end
end

# AMS 0.8 would return nil if the serializer was initialized with a nil
# resource.
def serializable_hash(adapter_options = nil,
options = {},
adapter_instance =
self.class.serialization_adapter_instance)
object.nil? ? nil : super
end
end

# AMS 0.8 would return nil if the serializer was initialized with a nil
# resource.
def serializable_hash(adapter_options = nil,
options = {},
adapter_instance =
self.class.serialization_adapter_instance)
object.nil? ? nil : super
end
end
end
Expand All @@ -90,12 +107,11 @@ end
Add this class to your app however you see fit. This is the class that your existing serializers
that inherit from `ActiveMode::Serializer` should inherit from.

### 3. Add `VersionEightCollectionSerializer`
#### Code
### 3. Add `ActiveModel::V08::CollectionSerializer`
```ruby
module ActiveModel
class Serializer
class VersionEightCollectionSerializer < CollectionSerializer
module V08
class CollectionSerializer < ActiveModel::Serializer::CollectionSerializer
# In AMS 0.8, passing an ArraySerializer instance with a `root` option
# properly nested the serialized resources within the given root.
# Ex.
Expand Down Expand Up @@ -155,14 +171,13 @@ module ActiveModel
end
```
Add this class to your app however you see fit. This is the class that existing uses of
`ActiveMode::ArraySerializer` should be changed to use.
`ActiveModel::ArraySerializer` should be changed to use.

### 4. Add `VersionEightAdapter`
#### Code
### 4. Add `ActiveModelSerializers::Adapter::V08Adapter`
```ruby
module ActiveModelSerializers
module Adapter
class VersionEightAdapter < Base
class V08Adapter < ActiveModelSerializers::Adapter::Base
def serializable_hash(options = nil)
options ||= {}

Expand All @@ -179,7 +194,7 @@ module ActiveModelSerializers

def serializable_hash_for_collection(options)
serializer.map do |s|
VersionEightAdapter.new(s, instance_options)
V08Adapter.new(s, instance_options)
.serializable_hash(options)
end
end
Expand Down Expand Up @@ -214,16 +229,16 @@ Add this class to your app however you see fit.
Add
```ruby
ActiveModelSerializers.config.adapter =
ActiveModelSerializers::Adapter::VersionEightAdapter
ActiveModelSerializers::Adapter::V08Adapter
```
to `config/active_model_serializer.rb` to configure AMS to use this
class as the default adapter.

### 5. Change inheritors of `ActiveModel::Serializer` to inherit from `ActiveModel::VersionEightSerializer`
### 5. Change inheritors of `ActiveModel::Serializer` to inherit from `ActiveModel::V08::Serializer`
Simple find/replace

### 6. Remove `private` keyword from serializers
Simple find/replace. This is required to allow the `ActiveModel::VersionEightSerializer`
Simple find/replace. This is required to allow the `ActiveModel::V08::Serializer`
to have proper access to the methods defined in the serializer.

You may be able to change the `private` to `protected`, but this is hasn't been tested yet.
Expand All @@ -233,8 +248,8 @@ This method is no longer supported in `0.10`.

`0.10` does a good job of discovering serializers for `ActiveRecord` objects.

### 8. Rename `ActiveModel::ArraySerializer` to `ActiveModel::Serializer::Version8CollectionSerializer`
Find/replace uses of `ActiveModel::ArraySerializer` with `ActiveModel::Serializer::Version8CollectionSerializer`.
### 8. Rename `ActiveModel::ArraySerializer` to `ActiveModel::V08::CollectionSerializer`
Find/replace uses of `ActiveModel::ArraySerializer` with `ActiveModel::V08::CollectionSerializer`.

Also, be sure to change the `each_serializer` keyword to `serializer` when calling making the replacement.

Expand Down

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