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', { :object_fields => 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
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 174 def self.documentation @documentation ||= exposures.inject({}) do |memo, value| unless value[1][:documentation].nil? || value[1][:documentation].empty? memo[value[0]] = value[1][:documentation] end memo end if superclass.respond_to? :documentation @documentation = superclass.documentation.merge(@documentation) end @documentation 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.
# File lib/grape_entity/entity.rb, line 125 def self.expose(*args, &block) options = args.last.is_a?(Hash) ? args.pop : {} options = (@block_options ||= []).inject({}){|final, step| final.merge!(step)}.merge(options) if args.size > 1 raise ArgumentError, "You may not use the :as option on multi-attribute exposures." if options[:as] raise ArgumentError, "You may not use block-setting on multi-attribute exposures." if block_given? end raise ArgumentError, "You may not use block-setting when also using format_with" if block_given? && options[:format_with].respond_to?(:call) options[:proc] = block if block_given? args.each do |attribute| exposures[attribute.to_sym] = options end end
Returns a hash of exposures that have been declared for this Entity or ancestors. The keys are symbolized references to methods on the containing object, the values are the options that were passed into expose.
# File lib/grape_entity/entity.rb, line 161 def self.exposures @exposures ||= {} if superclass.respond_to? :exposures @exposures = superclass.exposures.merge(@exposures) end @exposures 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 217 def self.format_with(name, &block) raise ArgumentError, "You must pass a block for formatters" unless block_given? formatters[name.to_sym] = block end
Returns a hash of all formatters that are registered for this and it's ancestors.
# File lib/grape_entity/entity.rb, line 223 def self.formatters @formatters ||= {} if superclass.respond_to? :formatters @formatters = superclass.formatters.merge(@formatters) end @formatters end
# File lib/grape_entity/entity.rb, line 305 def initialize(object, options = {}) @object, @options = object, options 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] 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.
# File lib/grape_entity/entity.rb, line 290 def self.represent(objects, options = {}) inner = if objects.respond_to?(:to_ary) objects.to_ary().map{|o| self.new(o, {:collection => true}.merge(options))} else self.new(objects, options) end root_element = if options.has_key?(:root) options[:root] else objects.respond_to?(:to_ary) ? @collection_root : @root end 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 272 def self.root(plural, singular=nil) @collection_root = plural @root = singular 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 152 def self.with_options(options) (@block_options ||= []).push(options) yield @block_options.pop end
# File lib/grape_entity/entity.rb, line 313 def documentation self.class.documentation end
# File lib/grape_entity/entity.rb, line 309 def exposures self.class.exposures end
# File lib/grape_entity/entity.rb, line 317 def formatters self.class.formatters 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 328 def serializable_hash(runtime_options = {}) return nil if object.nil? opts = options.merge(runtime_options || {}) exposures.inject({}) do |output, (attribute, exposure_options)| if (exposure_options.has_key?(:proc) || object.respond_to?(attribute)) && conditions_met?(exposure_options, opts) partial_output = value_for(attribute, opts) output[key_for(attribute)] = if partial_output.respond_to? :serializable_hash partial_output.serializable_hash(runtime_options) elsif partial_output.kind_of?(Array) && !partial_output.map {|o| o.respond_to? :serializable_hash}.include?(false) partial_output.map {|o| o.serializable_hash} else partial_output end end output end end
# File lib/grape_entity/entity.rb, line 349 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 354 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 390 def conditions_met?(exposure_options, options) if_condition = exposure_options[:if] unless_condition = exposure_options[:unless] case if_condition when Hash; if_condition.each_pair{|k,v| return false if options[k.to_sym] != v } when Proc; return false unless if_condition.call(object, options) when Symbol; return false unless options[if_condition] end case unless_condition when Hash; unless_condition.each_pair{|k,v| return false if options[k.to_sym] == v} when Proc; return false if unless_condition.call(object, options) when Symbol; return false if options[unless_condition] end true end
# File lib/grape_entity/entity.rb, line 361 def key_for(attribute) exposures[attribute.to_sym][:as] || attribute.to_sym end
# File lib/grape_entity/entity.rb, line 365 def value_for(attribute, options = {}) exposure_options = exposures[attribute.to_sym] if exposure_options[:proc] exposure_options[:proc].call(object, options) elsif exposure_options[:using] using_options = options.dup using_options.delete(:collection) using_options[:root] = nil exposure_options[:using].represent(object.send(attribute), using_options) elsif exposure_options[:format_with] format_with = exposure_options[:format_with] if format_with.is_a?(Symbol) && formatters[format_with] formatters[format_with].call(object.send(attribute)) elsif format_with.is_a?(Symbol) self.send(format_with, object.send(attribute)) elsif format_with.respond_to? :call format_with.call(object.send(attribute)) end else object.send(attribute) end end