A while back I wrote an article on Ruby’s #tap method, and a few places I’ve been using it and been seeing it used. One use that I mentioned in passing, I wanted to bring back up - because I’ve found its become something I do nearly every day.

That is, the combination of Object#tap and Symbol#to_proc.

What is Symbol#to_proc?

Symbol#to_proc is a shorthand for writing a full proc, so instead of:

names = ['john', 'kate']
names.map { |n| n.reverse }

You can write the much nicer:

names = ['john', 'kate']

Okay, but what is #tap again?

Tap can be written as:

class Object
  def tap(&:block)
    yield self

So we can tap into any method chain easily, for things like:

[1, 2, 3].reverse
[1, 2, 3].tap { |a| puts a.inspect }.reverse # no change in behavior

How does it all tie together?

A lot of times in Ruby, we have these “bang” form of methods, and they sometimes perform operations in-place or raise exception in non-happy paths. Let’s look at an example:

Array#uniq will always return self, so we can chain operations like:


Array#uniq! on the other hand, returns nil if there is nothing to be removed. So in order to write the same using the in-place version, we end up with:


Two lines! Sure, I can squash them into one with a semi-colon, but with Symbol#to_proc and Object#tap we can have it all:


The example is pretty simplified, but I’m sure you see how awesome this is. I use it with ActiveResource::Base#save! a lot too. Hope you like it!