Return Instance Variable in Object.new and keep Chained methods working

Question

I try to create a gem that performs a call to an API and returns an

HTTParty::Response

object using a minimal syntax like this:

MyGem.list_all 

#<HTTParty::Response:0x7fb859922908 parsed_response={...}>

My idea is to follow an ActiveRecord syntax style and allow chained methods like:

Mygem.list_all.total_count

> 22

The current code goes like this

module MyGem

  class << self

    def list_all

      @list_all ||= Get.new('list_all')

    end

  end



  class Get 

    def initialize(path)

      @get ||= get(path)

    end          



    def total_count

      @get['total_count']

    end



    def get(path) 

      HTTParty.get(url+path)

    end

  end

end

The code above works with the following call fetching the data from the

HTTParty::Response

and extracting the count value correctly.

Mygem.list_all.total_count

> 22

However when I call

MyGem.list_all

I get

MyGem::Get

object instead including its

@get

instance which contains the

HTTParty::Response

like this:

#<MyGem::Get:0x007fb26d10f4b0 @get=HTTParty response...

I understand

new

is returning its object and not the instance variable, my question is how can I still perform this call, get the HTTParty response and still have its chained (

total_count

) methods to work?

MyGem.list_all 

#<HTTParty::Response:0x7fb859922908 parsed_response={...}>

Answer 1

The rule of thumb is: whether you want to chain, return self from each single method, and implement everything you expect to retrieve from any subsequent method by delegation to self.

module MyGem
  class << self
    def list_all
      @list_all ||= Get.new('list_all')
    end

    class Get < BasicObject
      def initialize(path)
        @get ||= get(path)
      end
      HTTParty::Response.instance_methods(true).each do |m|
        meth = m # damn ruby closures
        define_method meth do |*args, &λ|
          @get.public_send(meth, *args, &λ)
        end
      end
    end
  end
end

Return Instance Variable in Object.new and keep Chained methods working

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