From: George Ogata <george.ogata@...>
Date: 2006-12-16T12:30:43+09:00
Subject: Re: using Proc and yield

On 12/16/06, Alber Eric <alberthier@yahoo.fr> wrote:
> OK, thank you for your quick answer
>
> I will just expose what I'm trying to do : I have four differents
> methods that are yielding strings. I want to use one or the other
> depending on the context but the rest of the process is the same, so I
> wrote something like that
>
> [...]
>
> What I'm looking for is a sort of function pointer.

Hi Eric,

Blocks can't take blocks in 1.8, so I think you'll need to resort
to methods if you do it this way.  Example:

  def methodI_foo_bar
    methodI{|s| yield "foo-#{s}-bar"}
  end
  def methodIII_oof_rab
    methodIII{|s| yield "oof-#{s}-rab"}
  end

  # First argument handling
  case arg1
  when 1
    p1 = method(:methodI)
  when 2
    p1 = method(:methodI_foo_bar)
  end

  # Second argument handling
  case arg2
  when 3
    p2 = method(:methodIII)
  when 4
    p2 = method(:methodIII_oof_rab)
  end

  p1.call { |i|
    p2.call { |j|
      process(i, j)
    }
  }

Or, perhaps more idiomatically:

  def methodI_foo_bar
    methodI{|s| yield "foo-#{s}-bar"}
  end
  def methodIII_oof_rab
    methodIII{|s| yield "oof-#{s}-rab"}
  end

  # First argument handling
  case arg1
  when 1
    m1 = :methodI
  when 2
    m1 = :methodI_foo_bar
  end

  # Second argument handling
  case arg2
  when 3
    m2 = :methodIII
  when 4
    m2 = :methodIII_oof_rab
  end

  send(m1) { |i|
    send(m2) { |j|
      process(i, j)
    }
  }

Does that help?