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', { :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

Attributes

object[R]
options[R]

Public Class Methods

documentation() click to toggle source

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
expose(*args, &block) click to toggle source

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
exposures() click to toggle source

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
format_with(name, &block) click to toggle source

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
formatters() click to toggle source

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
new(object, options = {}) click to toggle source
# File lib/grape_entity/entity.rb, line 305
def initialize(object, options = {})
  @object, @options = object, options
end
represent(objects, options = {}) click to toggle source
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
root(plural, singular=nil) click to toggle source

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
with_options(options) { || ... } click to toggle source

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

Public Instance Methods

as_json(runtime_options = {})
Alias for: serializable_hash
documentation() click to toggle source
# File lib/grape_entity/entity.rb, line 313
def documentation
  self.class.documentation
end
exposures() click to toggle source
# File lib/grape_entity/entity.rb, line 309
def exposures
  self.class.exposures
end
formatters() click to toggle source
# File lib/grape_entity/entity.rb, line 317
def formatters
  self.class.formatters
end
serializable_hash(runtime_options = {}) click to toggle source

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
Also aliased as: as_json
to_json(options = {}) click to toggle source
# 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
to_xml(options = {}) click to toggle source
# 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

Protected Instance Methods

conditions_met?(exposure_options, options) click to toggle source
# 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
key_for(attribute) click to toggle source
# File lib/grape_entity/entity.rb, line 361
def key_for(attribute)
  exposures[attribute.to_sym][:as] || attribute.to_sym
end
value_for(attribute, options = {}) click to toggle source
# 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