CODEWITHSUNDEEP
rubyclass
JP.
JP.

Reputation: 5594

Ruby forwarding method calls

I have an instance of a master class which generates instances of a subclass, these subclasses need to forward some method calls back to the master instance.

At the moment I have code looking something like this, but it feels like I should be able to do the same thing more efficiently (maybe with method_missing?)

class Master
  def initalize(mynum)
    @mynum = mynum
  end

  def one_thing(subinstance)
    "One thing with #{subinstance.var} from #{@mynum}"
  end

  def four_things(subinstance)
    "Four things with #{subinstance.var} from #{@mynum}"
  end

  def many_things(times,subinstance)
    "#{times} things with #{subinstance.var} from #{@mynum}"
  end

  def make_a_sub(uniqueness)
    Subthing.new(uniqueness,self)
  end


  class Subthing
    def initialize(uniqueness,master)
      @u = uniqueness
      @master = master
    end

    # Here I'm forwarding method calls
    def one_thing
      master.one_thing(self)
    end

    def four_things
      master.four_things(self)
    end

    def many_things(times)
      master.many_things(times,self)
    end
  end
end

m = Master.new(42)
s = m.make_a_sub("very")

s.one_thing === m.one_thing(s)

s.many_things(8) === m.many_things(8,s)

I hope you can see what's going on here. I would use method_missing, but I'm not sure how to cope with the possibility of some calls having arguments and some not (I can't really rearrange the order of the arguments to the Master methods either)

Thanks for reading!

Upvotes: 5

Views: 3998

Answers (1)

Chris McCauley
Chris McCauley

Reputation: 26363

Support for the Delegation Pattern


Delegate


Does the Delegate help here? It allows you to delegate methods to a second class

This library provides three different ways to delegate method calls to an object. The easiest to use is SimpleDelegator. Pass an object to the constructor and all methods supported by the object will be delegated. This object can be changed later.

Going a step further, the top level DelegateClass method allows you to easily setup delegation through class inheritance. This is considerably more flexible and thus probably the most common use for this library.

Finally, if you need full control over the delegation scheme, you can inherit from the abstract class Delegator and customize as needed. (If you find yourself needing this control, have a look at forwardable, also in the standard library. It may suit your needs better.)


Forwardable


There's also the forwardable library

This library allows you delegate method calls to an object, on a method by method basis. You can use Forwardable to setup this delegation at the class level, or SingleForwardable to handle it at the object level.

Upvotes: 7

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