class Grape::Entity
An Entity is a lightweight structure that allows you to easily represent data from your application in a consistent and abstracted way in your API. Entities can also provide documentation for the fields exposed.
@example Entity Definition
module API module Entities class User < Grape::Entity expose :first_name, :last_name, :screen_name, :location expose :field, documentation: { type: "string", desc: "describe the field" } expose :latest_status, using: API::Status, as: :status, unless: { collection: true } expose :email, if: { type: :full } expose :new_attribute, if: { version: 'v2' } expose(:name) { |model, options| [model.first_name, model.last_name].join(' ') } end end end
Entities are not independent structures, rather, they create *representations* of other Ruby objects using a number of methods that are convenient for use in an API. Once you've defined an Entity, you can use it in your API like this:
@example Usage in the API Layer
module API class Users < Grape::API version 'v2' desc 'User index', { params: API::Entities::User.documentation } get '/users' do @users = User.all type = current_user.admin? ? :full : :default present @users, with: API::Entities::User, type: type end end end
Constants
- OPTIONS
All supported options.
Attributes
Public Class Methods
# File lib/grape_entity/entity.rb, line 212 def self.can_unexpose? (@nesting_stack ||= []).empty? end
# File lib/grape_entity/entity.rb, line 216 def self.cannot_unexpose! fail "You cannot call 'unexpose` inside of nesting exposure!" end
Returns a hash, the keys are symbolized references to fields in the entity, the values are document keys in the entity's documentation key. When calling docmentation, any exposure without a documentation key will be ignored.
# File lib/grape_entity/entity.rb, line 238 def self.documentation @documentation ||= root_exposures.each_with_object({}) do |exposure, memo| if exposure.documentation && !exposure.documentation.empty? memo[exposure.key] = exposure.documentation end end end
This method is the primary means by which you will declare what attributes should be exposed by the entity.
@option options :as Declare an alias for the representation of this attribute. @option options :if When passed a Hash, the attribute will only be exposed if the
runtime options match all the conditions passed in. When passed a lambda, the lambda will execute with two arguments: the object being represented and the options passed into the representation call. Return true if you want the attribute to be exposed.
@option options :unless When passed a Hash, the attribute will be exposed if the
runtime options fail to match any of the conditions passed in. If passed a lambda, it will yield the object being represented and the options passed to the representation call. Return true to prevent exposure, false to allow it.
@option options :using This option allows you to map an attribute to another Grape
Entity. Pass it a Grape::Entity class and the attribute in question will automatically be transformed into a representation that will receive the same options as the parent entity when called. Note that arrays are fine here and will automatically be detected and handled appropriately.
@option options :proc If you pass a Proc into this option, it will
be used directly to determine the value for that attribute. It will be called with the represented object as well as the runtime options that were passed in. You can also just supply a block to the expose call to achieve the same effect.
@option options :documentation Define documenation for an exposed
field, typically the value is a hash with two fields, type and desc.
@option options :merge This option allows you to merge an exposed field to the root
# File lib/grape_entity/entity.rb, line 150 def self.expose(*args, &block) options = merge_options(args.last.is_a?(Hash) ? args.pop : {}) if args.size > 1 fail ArgumentError, 'You may not use the :as option on multi-attribute exposures.' if options[:as] fail ArgumentError, 'You may not use block-setting on multi-attribute exposures.' if block_given? end fail ArgumentError, 'You may not use block-setting when also using format_with' if block_given? && options[:format_with].respond_to?(:call) if block_given? if block.parameters.any? options[:proc] = block else options[:nesting] = true end end @documentation = nil @nesting_stack ||= [] # rubocop:disable Style/Next args.each do |attribute| exposure = Exposure.new(attribute, options) if @nesting_stack.empty? root_exposures << exposure else @nesting_stack.last.nested_exposures << exposure end # Nested exposures are given in a block with no parameters. if exposure.nesting? @nesting_stack << exposure block.call @nesting_stack.pop end end end
# File lib/grape_entity/entity.rb, line 196 def self.find_exposure(attribute) root_exposures.find_by(attribute) end
This allows you to declare a Proc in which exposures can be formatted with. It take a block with an arity of 1 which is passed as the value of the exposed attribute.
@param name [Symbol] the name of the formatter @param block [Proc] the block that will interpret the exposed attribute
@example Formatter declaration
module API module Entities class User < Grape::Entity format_with :timestamp do |date| date.strftime('%m/%d/%Y') end expose :birthday, :last_signed_in, format_with: :timestamp end end end
@example Formatters are available to all decendants
Grape::Entity.format_with :timestamp do |date| date.strftime('%m/%d/%Y') end
# File lib/grape_entity/entity.rb, line 272 def self.format_with(name, &block) fail ArgumentError, 'You must pass a block for formatters' unless block_given? formatters[name.to_sym] = block end
Returns all formatters that are registered for this and it's ancestors @return [Hash] of formatters
# File lib/grape_entity/entity.rb, line 110 def formatters @formatters ||= {} end
# File lib/grape_entity/entity.rb, line 119 def self.inherited(subclass) subclass.root_exposure = root_exposure.dup subclass.formatters = formatters.dup end
Merges the given options with current block options.
@param options [Hash] Exposure options.
# File lib/grape_entity/entity.rb, line 508 def self.merge_options(options) opts = {} merge_logic = proc do |key, existing_val, new_val| if [:if, :unless].include?(key) if existing_val.is_a?(Hash) && new_val.is_a?(Hash) existing_val.merge(new_val) elsif new_val.is_a?(Hash) (opts["#{key}_extras".to_sym] ||= []) << existing_val new_val else (opts["#{key}_extras".to_sym] ||= []) << new_val existing_val end else new_val end end @block_options ||= [] opts.merge @block_options.inject({}) { |final, step| final.merge(step, &merge_logic) }.merge(valid_options(options), &merge_logic) end
# File lib/grape_entity/entity.rb, line 427 def initialize(object, options = {}) @object = object @delegator = Delegator.new object @options = if options.is_a? Options options else Options.new options end end
This allows you to present a collection of objects.
@param ::present_collection [true or false] when true all objects will be available as
items in your presenter instead of wrapping each object in an instance of your presenter. When false (default) every object in a collection to present will be wrapped separately into an instance of your presenter.
@param collection_name [Symbol] the name of the collection accessor in your entity object.
Default :items
@example Entity Definition
module API module Entities class User < Grape::Entity expose :id end class Users < Grape::Entity present_collection true expose :items, as: 'users', using: API::Entities::User expose :version, documentation: { type: 'string', desc: 'actual api version', required: true } def version options[:version] end end end end
@example Usage in the API Layer
module API class Users < Grape::API version 'v2' # this will render { "users" : [ { "id" : "1" }, { "id" : "2" } ], "version" : "v2" } get '/users' do @users = User.all present @users, with: API::Entities::Users end # this will render { "user" : { "id" : "1" } } get '/users/:id' do @user = User.find(params[:id]) present @user, with: API::Entities::User end end end
# File lib/grape_entity/entity.rb, line 372 def self.present_collection(present_collection = false, collection_name = :items) @present_collection = present_collection @collection_name = collection_name end
This convenience method allows you to instantiate one or more entities by passing either a singular or collection of objects. Each object will be initialized with the same options. If an array of objects is passed in, an array of entities will be returned. If a single object is passed in, a single entity will be returned.
@param objects [Object or Array] One or more objects to be represented. @param options [Hash] Options that will be passed through to each entity
representation.
@option options :root [String or false] override the default root name set for the entity.
Pass nil or false to represent the object or objects with no root name even if one is defined for the entity.
@option options :serializable [true or false] when true a serializable Hash will be returned
@option options :only [Array] all the fields that should be returned @option options :except [Array] all the fields that should not be returned
# File lib/grape_entity/entity.rb, line 394 def self.represent(objects, options = {}) if objects.respond_to?(:to_ary) && ! @present_collection root_element = root_element(:collection_root) inner = objects.to_ary.map { |object| new(object, options.reverse_merge(collection: true)).presented } else objects = { @collection_name => objects } if @present_collection root_element = root_element(:root) inner = new(objects, options).presented end root_element = options[:root] if options.key?(:root) root_element ? { root_element => inner } : inner end
This allows you to set a root element name for your representation.
@param plural [String] the root key to use when representing
a collection of objects. If missing or nil, no root key will be used when representing collections of objects.
@param singular [String] the root key to use when representing
a single object. If missing or nil, no root key will be used when representing an individual object.
@example Entity Definition
module API module Entities class User < Grape::Entity root 'users', 'user' expose :id end end end
@example Usage in the API Layer
module API class Users < Grape::API version 'v2' # this will render { "users" : [ { "id" : "1" }, { "id" : "2" } ] } get '/users' do @users = User.all present @users, with: API::Entities::User end # this will render { "user" : { "id" : "1" } } get '/users/:id' do @user = User.find(params[:id]) present @user, with: API::Entities::User end end end
# File lib/grape_entity/entity.rb, line 316 def self.root(plural, singular = nil) @collection_root = plural @root = singular end
This method returns the entity's root or collection root node, or its parent's @param root_type: either :collection_root or just :root
# File lib/grape_entity/entity.rb, line 411 def self.root_element(root_type) if instance_variable_get("@#{root_type}") instance_variable_get("@#{root_type}") elsif superclass.respond_to? :root_element superclass.root_element(root_type) end end
# File lib/grape_entity/entity.rb, line 102 def root_exposure @root_exposure ||= Exposure.new(nil, nesting: true) end
Returns exposures that have been declared for this Entity on the top level. @return [Array] of exposures
# File lib/grape_entity/entity.rb, line 192 def self.root_exposures root_exposure.nested_exposures end
# File lib/grape_entity/entity.rb, line 200 def self.unexpose(*attributes) cannot_unexpose! unless can_unexpose? @documentation = nil root_exposures.delete_by(*attributes) end
# File lib/grape_entity/entity.rb, line 206 def self.unexpose_all cannot_unexpose! unless can_unexpose? @documentation = nil root_exposures.clear end
Raises an error if the given options include unknown keys. Renames aliased options.
@param options [Hash] Exposure options.
# File lib/grape_entity/entity.rb, line 537 def self.valid_options(options) options.keys.each do |key| fail ArgumentError, "#{key.inspect} is not a valid option." unless OPTIONS.include?(key) end options[:using] = options.delete(:with) if options.key?(:with) options end
Set options that will be applied to any exposures declared inside the block.
@example Multi-exposure if
class MyEntity < Grape::Entity with_options if: { awesome: true } do expose :awesome, :sweet end end
# File lib/grape_entity/entity.rb, line 229 def self.with_options(options) (@block_options ||= []).push(valid_options(options)) yield @block_options.pop end
Public Instance Methods
# File lib/grape_entity/entity.rb, line 480 def delegate_attribute(attribute) if respond_to?(attribute, true) send(attribute) else delegator.delegate(attribute) end end
# File lib/grape_entity/entity.rb, line 445 def documentation self.class.documentation end
# File lib/grape_entity/entity.rb, line 472 def exec_with_attribute(attribute, &block) instance_exec(delegate_attribute(attribute), &block) end
# File lib/grape_entity/entity.rb, line 468 def exec_with_object(options, &block) instance_exec(object, options, &block) end
# File lib/grape_entity/entity.rb, line 449 def formatters self.class.formatters end
# File lib/grape_entity/entity.rb, line 419 def presented if options[:serializable] serializable_hash else self end end
# File lib/grape_entity/entity.rb, line 441 def root_exposure self.class.root_exposure end
# File lib/grape_entity/entity.rb, line 437 def root_exposures self.class.root_exposures end
The serializable hash is the Entity's primary output. It is the transformed hash for the given data model and is used as the basis for serialization to JSON and other formats.
@param runtime_options [Hash] Any options you pass in here will be known to the entity
representation, this is where you can trigger things from conditional options etc.
# File lib/grape_entity/entity.rb, line 460 def serializable_hash(runtime_options = {}) return nil if object.nil? opts = options.merge(runtime_options || {}) root_exposure.serializable_value(self, opts) end
# File lib/grape_entity/entity.rb, line 490 def to_json(options = {}) options = options.to_h if options && options.respond_to?(:to_h) MultiJson.dump(serializable_hash(options)) end
# File lib/grape_entity/entity.rb, line 495 def to_xml(options = {}) options = options.to_h if options && options.respond_to?(:to_h) serializable_hash(options).to_xml(options) end
# File lib/grape_entity/entity.rb, line 476 def value_for(key, options = Options.new) root_exposure.valid_value_for(key, self, options) end