From: Stefano Crocco <stefano.crocco@...>
Date: 2009-01-29T05:21:34+09:00
Subject: Re: yield vs. return

Alle mercoledì 28 gennaio 2009, klochner ha scritto:
> I couldn't find any meaty discussions on this topic, so maybe it's
> worth a post.
>
> Does it make sense to use yield at the end of a function, where you're
> essentially
> using yield to replace a return value?  For example:
>
> def returnfoo
>   return foo
> end
>
> vs.
>
> def yieldfoo
>   yield foo
> end
>
> I see a lot of ruby programmers doing the latter, but consider the
> former to
> be more straightforward.  There are a lot of cases where yielding is
> more elegant
> than return, but I don't consider this to be one of them.  Anyone care
> to weigh in?

yield and return do completely different things, and you can't use one in 
place of the other. return tells ruby to stop executing the method and return 
its argument to the caller. yield tells ruby to call the block passed to the 
method, giving it its argument. yield will produce an error if the method 
wasn't called with a block:

def test_yield
  yield 43
end
test_yield # notice that no block was passed to the method
=> LocalJumpError: no block given

In ruby, there's no need to put a return at the end of a method, as the method 
will always return the value of the last expression. This means that a method 
defined this way:

def test_return
  return 4
end

will give exactly the same result as a method defined this way:

def test_no_return
  4
end

Can you give an example of a situation where you think yield is used in place 
of return? This way, we'll be able to understand better what you're referring 
to and make more useful comments.

Stefano