From: Nasir Khan <rubylearner@...>
Date: 2007-08-27T11:15:01+09:00
Subject: how to check for block in an evaled method?

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Consider the snippet -

 class B
   def set
     B.class_eval do
        define_method(:a) do |arg|
          if block_given?
            yield
          else
            "hello"
          end
        end
      end
    end
  end

The intention is that block_given? would tell me if the new method a() is
invoked with a block or not.
Now I run this

irb(main):057:0* y = B.new
=> #<B:0x2caf2b8>

irb(main):059:0> y.set
=> #<Proc:0x02cb6784@(irb):45>
irb(main):060:0> y.a
(irb):45: warning: multiple values for a block parameter (0 for 1)
        from (irb):60
=> "hello"

Now if I use with a block

irb(main):061:0> y.a {"bye"}
(irb):45: warning: multiple values for a block parameter (0 for 1)
        from (irb):61
=> "hello"

Oops doesnt work !

Actually the block is being evaled when the method is being created -

irb(main):062:0> y.set {"bye"}
=> #<Proc:0x02cb6784@(irb):45>
irb(main):063:0> y.a
(irb):45: warning: multiple values for a block parameter (0 for 1)
        from (irb):63
=> "bye"

I get that. But the question is, is there a way to check for a block and
then yield in a defined method, as was my naive intention?


Thanks
Nasir

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