SimpleRepresenter

Simple solution to represent your objects as hash or json.

Instalation

Add this line to your application's Gemfile:

gem 'simple_representer'

And then execute:

$ bundle install

Usage

Create a class that inherits from SimpleRepresenter::Representer and define your representation using property (to access methods defined in represented object) and computed (to use methods defined inside representer) class methods.

class UserRepresenter < SimpleRepresenter::Representer
    property :id
    computed :full_name
    computed :is_active

    def full_name
      "#{represented.first_name} #{represented.last_name}"
    end

    def is_active
      !represented.activated_at.nil?
    end
end

Pass your object as argument in initializer and call to_h/to_hash or to_json. You can also represent hashes like normal objects (see: SimpleRepresenter::CallableHash)

user = User.find(1)
UserRepresenter.new(user).to_json
 => "{\"id\":1,\"full_name\":\"Jon Doe\",\"is_active\":false}"
UserRepresenter.new(user).to_hash
 => {:id=>1, :full_name=>"Jon Doe", :is_active=>false}

Collections

To use SimpleRepresenter with collection of objects use for_collection method:

 UserRepresenter.for_collection(users).to_json
 => "[{\"id\":1,\"full_name\":\"Jon Doe\",\"is_active\":false},{\"id\":2,\"full_name\":\"Jon Wick\",\"is_active\":true}]"

Options

Both property and computed have following options:

• if to make execution dependent on condition: ruby property :full_name, if: -> { first_name && last_name }
• as to rename field in representation: ruby property :is_active?, as: :is_active
• default to set default value: ruby property :name, default: 'Paladin'
• render_nil to render or skip nil value (default is false): ruby # will render { name: nil } if name is nil property :name, render_nil: true
• representer to use different representer for nested objects. If it's an array for_collection will be automatically called. ruby property :comments, representer: CommentsRepresenter

Additional arguments

You can pass additional arguments to initializer. You can access them inside computed methods or any other place using options:

class UserRepresenter < SimpleRepresenter::Representer
    property :id
    property :full_name, if: -> { options[:display_name] }
end

user = OpenStruct.new({ id: 5, full_name: 'Batman' })
UserRepresenter.new(user, display_name: false).to_json
 => "{\"id\":5}"

You can set default options for properties by using defaults:

class UserRepresenter < SimpleRepresenter::Representer
    defaults render_nil: true # render nil properties
    property :id
end

Migrating from Roar

Replace all occurrences of exec_context: :decorator to computed:

property :full_name, exec_context: :decorator
=>
computed :full_name

Replace decorator with representer and collection with computed or property for nested objects:

collection :songs, decorator: SongRepresenter
=>
property :songs, representer: SongRepresenter

Specs

Just run rspec.