Delegate is actually an alias

JSONAPI::Resource と attributes オプションの委譲処理から始め、issue にある Ruby と Rails の委譲例とその動作を比較します。delegate オプションが説明どおりにメソッドを委譲先オブジェクトへ転送するか、またはエイリアスのような動作が明確に文書化されていれば完了です。

When working with the gem and trying to look at how to hide underlying models I came across the delegate option which is available on a resource.

Using this option I expected the same result as with the definitions provided in both ruby and rails. When I delegate a method to something, it calls the method being delegated on that something.

An example:

class Bar
  attr_accessor :name

  def initialize
    @name = "Test"
  end
end

class Foo
  extend Forwardable
  attr_accessor :bar

  def initialize
    @bar = Bar.new
  end

  def_delegator :@bar, :name
end

Foo.new.name            # => "Test"
foo = Foo.new
foo.bar.name = "Demo"
foo.name                # => "Demo"

This passes the delegate method along to the object @bar.

Now looking at the way it is defined in JSONAPI::Resource we have the following option:

class Bar
  attr_accessor :name

  def initialize
    @name = "Test"
  end
end

class Foo
  attr_accessor :bar

  def initialize
    @bar = Bar.new
  end
end

class FooResource < JSONAPI::Resource
  attributes :name, delegate: :bar
end

FooResource.new(Foo.new, {}).name  # => <Bar:0x007fd288c69708 @name="Test">

As you can see when calling name on the resource it gives me back the object Bar instead of calling the method name on the Bar object. This is more in line with how alias works instead of how delegate works.

It might be an idea to make this clearer in the documentation to prevent any confusion, and it maybe an idea in the future to modify this behaviour to be the same as how ruby and rails handle this.