From: Phrogz <phrogz@...>
Date: 2010-07-26T00:40:05+09:00
Subject: Re: assign blocks to variables

On Jul 25, 8:58 am, poseid <mulder.patr...@gmail.com> wrote:
> If you want to work on a function that takes a block as input, is it
> possible to assign the block to a variable?

You can capture a block parameter passed to a method using an
ampersand name at the end. You can pass a proc as a block to a method
by throwing an ampersand before it. There are also other ways to
create a proc value, such as using the 'proc' or 'lambda' methods, or
the arrow syntax available in 1.9:


>> def capture_block(&my_block); my_block; end
>> def with42; yield 42; end
>> b1 = capture_block{ |n| puts "N is #{n}" }
=> #<Proc:0x00000100844200@(irb):3>

>> with42( &b1 )
N is 42

>> b2 = proc{ |n| puts "I said, it is #{n}" }
=> #<Proc:0x00000100c061b0@(irb):5>

>> with42( &b2 )
I said, it is 42

>> b3 = ->(n){ puts "Oh my #{n}" }
=> #<Proc:0x00000100be7cf0@(irb):11 (lambda)>
>> with42( &b3 )
Oh my 42