Using yield inside define_method in Ruby

Question

Is it possible to make yield keyword work inside a block given to define_method? Simple example:

class Test
  define_method :test do |&b         


        

Answer 1

You cannot use yield inside a define_method block. This is because blocks are captured by closures, observe:

def hello
  define_singleton_method(:bye) { yield }
end

hello { puts "hello!" }

bye {  puts "bye!" } #=> "hello!"

I don't think your users will mind not being able to use 'yield' in the way you state ---- the syntax is nothing like ordinary Ruby method definition syntax so there is unlikely to be any confusion.

More information on why you cannot pass blocks implicitly to methods found here: http://banisterfiend.wordpress.com/2010/11/06/behavior-of-yield-in-define_method/

Answer 2

I think this is what you're looking for:

class Test
  define_method :test do |&b|
    b.call
  end
end

Test.new.test {
  puts "Hi!"
}

More at http://coderrr.wordpress.com/2008/10/29/using-define_method-with-blocks-in-ruby-18/