Recursive method with condition

Question

Using Ruby 2.0. Here's my code:

module Test
  class A
    def initialize(x)
      @x = x
      foo
    end

    def foo
      p @x
      update(@x) # only if it's a Test::C object or called from Test::C
    end
  end
end

module Test
  class B < A
    def foo
      @x += 2
      super
    end
  end
end

module Test
  class C < A
    def foo
      @x += 1
      super
    end
  end
end

def update(x)
  if x > 100
    Test::B.new(x)
  else
    Test::C.new(x)
  end
end

x = 100
update(x)

Here's what I am trying to achieve:

In Test::A#foo, update(@x) should be called only if it were called from Test::C#foo or it's a Test::C object.

The first time update(x) is called, x = 100, so the operation should +1 and then move on to Test::B#foo once. How do I achieve this?

This question is very unclear since you specify update at the highest level but then call it inside Test::A#foo and you never actually call the foo method anywhere so nothing is actually happening here. If Test::A#foo should only be called from Test::C#foo then that is where you implement it. If Test::A does not need to update and Test::B does not need to update why would you put the logic at such a high level? Also this does not seem to have anything to do with recursion at all — engineersmnky
– engineersmnky, Commented Jun 10, 2015 at 18:36

tadman · Accepted Answer · 2015-06-10 18:12:26Z

1

The parent class should not have to care about subclasses. This design you have here implies it needs to know, which is broken and over-complicates things.

In any case, if you do need to trap certain cases:

case (self)
when Test::A, Test::B
  # ... Do stuff
  update(@x)
end

If Test::A and Test::B care about that operation, they should call it when necessary:

def foo
  @x += 1
  super
  update(x)
end

answered Jun 10, 2015 at 18:12

tadman

212k23 gold badges237 silver badges266 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Victor Over a year ago

I could probably do this update(@x) if self.is_a?(Test::C), but is there a better way to write it? Actually don't need to worry about the value, but my end goal is: everytime Test::C is initialized, it should run foo based on Test::C once, then run it again as Test::B.

tadman Over a year ago

While you can do that, it doesn't mean you should. Generally it's best to put class-specific logic in the subclass and have the parent class unconcerned with those details. Translating your goal to Ruby, that'd imply you do something inside Test::C#initialize, for example.

Collectives™ on Stack Overflow

Recursive method with condition

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related