Naked Splats Pass Blocks
Published 21 Nov 2015. Tags: ruby.
Occasionally in Ruby I want to add some extra behavior to a method in a
subclass, like creating an extra instance variable or triggering a callback. In
cases like that, I generally want to receive the same arguments as in the
superclass and pass them along through a call to
super. Ruby makes that pretty
easy; I can put a “naked splat” in the arguments list and
automagically pass along those same arguments:
class B < A def initialize(*) super do_an_extra_thing end end
However, I can never remember if
(*) passes along a block argument. Well,
it does! Here’s proof:
class A def upcase_and_call_block(bar, &block) puts bar.upcase block.call end end class B < A def upcase_and_call_block(*) super puts "Done!" end end B.new.upcase_and_call_block("test string") do puts "Called the block!" end
The output of this is:
TEST STRING Called the block! Done!
So, there ya go: the naked splat passes blocks.
I only need to know this once a year or so. I inevitably forget it, try to search for it, find nothing, and have to repeat the experiment above. Maybe I’ll find this article in the future!