Pass block passed to method to another method in Ruby
You can reference the block explicitly
def discard(&block)
self - self.keep(&block)
end
or implicitly
def discard
self - self.keep(&Proc.new {})
end
In your case, I would suggest the first approach.
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 block
def discard(&block)
self - keep(&block)
end
# passes on the block and fails if no block given
def discard
self - keep(&proc)
end
Both 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.