I was a PHP programmer before, I got used to 'echo' when trying to debug PHP application. That's why when migrating to Ruby from PHP, I used pp a lot. Although it just prints to console, it helps a lot.

But I've been wondering all this while, sometimes I got an application error,

undefined method 'pp'

while trying to pretty-print an object on Rails.

I never bothered to find out why, until today where I just happen to.

It turns out we have to

require 'PP'

on our code to make it works. Duh!

And make sure you use lowercase 'pp' if you are in a linux environment, otherwise it will say

No such file to load