Class: ActiveModel::Serializer

Inherits:
Object
  • Object
show all
Extended by:
ActiveSupport::DescendantsTracker
Includes:
Serializable, Caching
Defined in:
lib/active_model/serializer.rb,
lib/active_model/serializer/caching.rb,
lib/active_model/serializer/version.rb,
lib/active_model/serializer/associations.rb

Overview

Active Model Serializer

Provides a basic serializer implementation that allows you to easily control how a given object is going to be serialized. On initialization, it expects two objects as arguments, a resource and options. For example, one may do in a controller:

PostSerializer.new(@post, scope: current_user).to_json

The object to be serialized is the @post and the current user is passed in for authorization purposes.

We use the scope to check if a given attribute should be serialized or not. For example, some attributes may only be returned if current_user is the author of the post:

class PostSerializer < ActiveModel::Serializer
  attributes :title, :body
  has_many :comments

  private

  def attributes
    hash = super
    hash.merge!(email: post.email) if author?
    hash
  end

  def author?
    post.author == scope
  end
end

Defined Under Namespace

Modules: Caching Classes: Association, IncludeError

Constant Summary collapse

INCLUDE_METHODS = 
{}
INSTRUMENT = 
{ serialize: :"serialize.serializer", associations: :"associations.serializer" }
VERSION = 
"0.8.2"

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Caching

#serialize, #to_json

Constructor Details

#initialize(object, options = {}) ⇒ Serializer

Returns a new instance of Serializer.



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# File 'lib/active_model/serializer.rb', line 296

def initialize(object, options={})
  @object, @options = object, options

  scope_name = @options[:scope_name]
  if scope_name && !respond_to?(scope_name)
    self.class.class_eval do
      define_method scope_name, lambda { scope }
    end
  end
end

Instance Attribute Details

#object ⇒ Object (readonly)

Returns the value of attribute object.



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# File 'lib/active_model/serializer.rb', line 294

def object
  @object
end

#options ⇒ Object (readonly)

Returns the value of attribute options.



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# File 'lib/active_model/serializer.rb', line 294

def options
  @options
end

Class Method Details

.associate(klass, attrs) ⇒ Object

:nodoc:



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# File 'lib/active_model/serializer.rb', line 119

def associate(klass, attrs) #:nodoc:
  options = attrs.extract_options!
  self._associations = _associations.dup

  attrs.each do |attr|
    unless method_defined?(attr)
      define_method attr do
        object.send attr
      end
    end

    define_include_method attr

    self._associations[attr] = [klass, options]
  end
end

.attribute(attr, options = {}) ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 96

def attribute(attr, options={})
  self._attributes = _attributes.merge(attr.is_a?(Hash) ? attr : {attr => options[:key] || attr.to_s.gsub(/\?$/, '').to_sym})

  attr = attr.keys[0] if attr.is_a? Hash

  unless method_defined?(attr)
    define_method attr do
      object.read_attribute_for_serialization(attr.to_sym)
    end
  end

  define_include_method attr

  # protect inheritance chains and open classes
  # if a serializer inherits from another OR
  #  attributes are added later in a classes lifecycle
  # poison the cache
  define_method :_fast_attributes do
    raise NameError
  end

end

.attributes(*attrs) ⇒ Object

Define attributes to be used in the serialization.



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# File 'lib/active_model/serializer.rb', line 83

def attributes(*attrs)

  self._attributes = _attributes.dup

  attrs.each do |attr|
    if Hash === attr
      attr.each {|attr_real, key| attribute(attr_real, key: key) }
    else
      attribute attr
    end
  end
end

.build_json(controller, resource, options) ⇒ Object

Used internally to create a new serializer object based on controller settings and options for a given resource. These settings are typically set during the request lifecycle or by the controller class, and should not be manually defined for this method.



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# File 'lib/active_model/serializer.rb', line 264

def build_json(controller, resource, options)
  default_options = controller.send(:default_serializer_options) || {}
  options = default_options.merge(options || {})

  serializer = options.delete(:serializer) ||
    (resource.respond_to?(:active_model_serializer) &&
     resource.active_model_serializer)

  return serializer unless serializer

  if resource.respond_to?(:to_ary)
    unless serializer <= ActiveModel::ArraySerializer
      raise ArgumentError.new("#{serializer.name} is not an ArraySerializer. " +
                              "You may want to use the :each_serializer option instead.")
    end

    if options[:root] != false && serializer.root != false
      # the serializer for an Array is ActiveModel::ArraySerializer
      options[:root] ||= serializer.root || controller.controller_name
    end
  end

  options[:scope] = controller.serialization_scope unless options.has_key?(:scope)
  options[:scope_name] = controller._serialization_scope unless options.has_key?(:scope_name)
  options[:url_options] = controller.url_options

  serializer.new(resource, options)
end

.cached(value = true) ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 78

def cached(value = true)
  self.perform_caching = value
end

.define_include_method(name) ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 136

def define_include_method(name)
  method = "include_#{name}?".to_sym

  INCLUDE_METHODS[name] = method

  unless method_defined?(method)
    define_method method do
      true
    end
  end
end

.embed(type, options = {}) ⇒ Object

Define how associations should be embedded.

embed :objects               # Embed associations as full objects
embed :ids                   # Embed only the association ids
embed :ids, include: true    # Embed the association ids and include objects in the root



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# File 'lib/active_model/serializer.rb', line 249

def embed(type, options={})
  self._embed = type
  self._root_embed = true if options[:include]
end

.has_many(*attrs) ⇒ Object

Defines an association in the object should be rendered.

The serializer object should implement the association name as a method which should return an array when invoked. If a method with the association name does not exist, the association name is dispatched to the serialized object.



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# File 'lib/active_model/serializer.rb', line 154

def has_many(*attrs)
  associate(Association::HasMany, attrs)
end

.has_one(*attrs) ⇒ Object

Defines an association in the object should be rendered.

The serializer object should implement the association name as a method which should return an object when invoked. If a method with the association name does not exist, the association name is dispatched to the serialized object.



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# File 'lib/active_model/serializer.rb', line 164

def has_one(*attrs)
  associate(Association::HasOne, attrs)
end

.model_class ⇒ Object

The model class associated with this serializer.



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# File 'lib/active_model/serializer.rb', line 239

def model_class
  name.sub(/Serializer$/, '').constantize
end

.root(name) ⇒ Object Also known as: root=

Defines the root used on serialization. If false, disables the root.



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# File 'lib/active_model/serializer.rb', line 255

def root(name)
  self._root = name
end

.schema ⇒ Object

Return a schema hash for the current serializer. This information can be used to generate clients for the serialized output.

The schema hash has two keys: attributes and associations.

The attributes hash looks like this:

{ name: :string, age: :integer }

The associations hash looks like this:

{ posts: { has_many: :posts } }

If :key is used:

class PostsSerializer < ActiveModel::Serializer
  has_many :posts, key: :my_posts
end

the hash looks like this:

{ my_posts: { has_many: :posts }

This information is extracted from the serializer’s model class, which is provided by SerializerClass.model_class.

The schema method uses the columns_hash and reflect_on_association methods, provided by default by ActiveRecord. You can implement these methods on your custom models if you want the serializer’s schema method to work.

TODO: This is currently coupled to Active Record. We need to figure out a way to decouple those two.



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# File 'lib/active_model/serializer.rb', line 200

def schema
  klass = model_class
  columns = klass.columns_hash

  attrs = {}
  _attributes.each do |name, key|
    if column = columns[name.to_s]
      attrs[key] = column.type
    else
      # Computed attribute (method on serializer or model). We cannot
      # infer the type, so we put nil, unless specified in the attribute declaration
      if name != key
        attrs[name] = key
      else
        attrs[key] = nil
      end
    end
  end

  associations = {}
  _associations.each do |attr, (association_class, options)|
    association = association_class.new(attr, options)

    if model_association = klass.reflect_on_association(association.name)
      # Real association.
      associations[association.key] = { model_association.macro => model_association.name }
    else
      # Computed association. We could infer has_many vs. has_one from
      # the association class, but that would make it different from
      # real associations, which read has_one vs. belongs_to from the
      # model.
      associations[association.key] = nil
    end
  end

  { attributes: attrs, associations: associations }
end

Instance Method Details

#as_json(args = {}) ⇒ Object

Returns a json representation of the serializable object including the root.



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# File 'lib/active_model/serializer.rb', line 325

def as_json(args={})
  super(root: args.fetch(:root, options.fetch(:root, root_name)))
end

#attributes ⇒ Object

Returns a hash representation of the serializable object attributes.



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# File 'lib/active_model/serializer.rb', line 420

def attributes
  _fast_attributes
  rescue NameError
    method = "def _fast_attributes\n"

    method << "  h = {}\n"

    _attributes.each do |name,key|
      method << "  h[:\"#{key}\"] = read_attribute_for_serialization(:\"#{name}\") if include?(:\"#{name}\")\n"
    end
    method << "  h\nend"

    self.class.class_eval method
    _fast_attributes
end

#include!(name, options = {}) ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 354

def include!(name, options={})
  hash = @options[:hash]
  unique_values = @options[:unique_values] ||= {}

  node = options[:node] ||= @node
  value = options[:value]

  if options[:include] == nil
    if @options.key?(:include)
      options[:include] = @options[:include].include?(name)
    elsif @options.include?(:exclude)
      options[:include] = !@options[:exclude].include?(name)
    end
  end

  klass, klass_options = _associations[name]
  association_class =
    if klass
      options = klass_options.merge options
      klass
    elsif value.respond_to?(:to_ary)
      Association::HasMany
    else
      Association::HasOne
    end

  options = default_embed_options.merge!(options)
  options[:value] ||= send(name)
  association = association_class.new(name, options, self.options)

  if association.embed_ids?
    node[association.key] = association.serialize_ids

    if association.embed_in_root? && hash.nil?
      raise IncludeError.new(self.class, association.name)
    elsif association.embed_in_root? && association.embeddable?
      merge_association hash, association.root, association.serializables, unique_values
    end
  elsif association.embed_objects?
    node[association.key] = association.serialize
  end
end

#include?(name) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_model/serializer.rb', line 348

def include?(name)
  return false if @options.key?(:only) && !Array(@options[:only]).include?(name)
  return false if @options.key?(:except) && Array(@options[:except]).include?(name)
  send INCLUDE_METHODS[name]
end

#include_associations! ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 342

def include_associations!
  _associations.each_key do |name|
    include!(name) if include?(name)
  end
end

#instrument(name, payload = {}, &block) ⇒ Object

Use ActiveSupport::Notifications to send events to external systems. The event name is: name.class_name.serializer



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# File 'lib/active_model/serializer.rb', line 445

def instrument(name, payload = {}, &block)
  event_name = INSTRUMENT[name]
  ActiveSupport::Notifications.instrument(event_name, payload, &block)
end

#merge_association(hash, key, serializables, unique_values) ⇒ Object

In some cases, an Array of associations is built by merging the associated content for all of the children. For instance, if a Post has_many comments, which has_many tags, the top-level :tags key will contain the merged list of all tags for all comments of the post.

In order to make this efficient, we store a :unique_values hash containing a unique list of all of the objects that are already in the Array. This avoids the need to scan through the Array looking for entries every time we want to merge a new list of values.



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# File 'lib/active_model/serializer.rb', line 406

def merge_association(hash, key, serializables, unique_values)
  already_serialized = (unique_values[key] ||= {})
  serializable_hashes = (hash[key] ||= [])

  serializables.each do |serializable|
    unless already_serialized.include? serializable.object
      already_serialized[serializable.object] = true
      serializable_hashes << serializable.serializable_hash
    end
  end
end

#root_name ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 307

def root_name
  return false if self._root == false

  class_name = self.class.name.demodulize.underscore.sub(/_serializer$/, '').to_sym unless self.class.name.blank?

  if self._root == true
    class_name
  else
    self._root || class_name
  end
end

#scope ⇒ Object

Returns options



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# File 'lib/active_model/serializer.rb', line 437

def scope
  @options[:scope]
end

#serializable_hash ⇒ Object

Returns a hash representation of the serializable object without the root.



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# File 'lib/active_model/serializer.rb', line 335

def serializable_hash
  return nil if @object.nil?
  @node = attributes
  include_associations! if _embed
  @node
end

#serialize_object ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 329

def serialize_object
  serializable_hash
end

#url_options ⇒ Object 



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# File 'lib/active_model/serializer.rb', line 319

def url_options
  @options[:url_options] || {}
end