Pass block passed to method to another method in Ruby
In the second example, &Proc.new {} doesn't pass a block, it creates a new empty one. One should omit {} and write it as self.keep(&Proc.new) or just keep(&proc) as self. is redundant and proc is the recommended synonym for Proc.new:
# passes on the block or the absence of a blockdef discard(&block) self - keep(&block)end# passes on the block and fails if no block givendef discard self - keep(&proc)endBoth Proc.new and proc without a block use the block of the current method.
&proc will fail if discard doesn't get a block. So the first example is the best if you want to pass the block or the absence of a block (&nil passes no block at all). The second example (as I changed it) is the best if missing block is an error.
In both cases, each time 'discard' is called, a new 'Proc' object is created, and it's not free.