Ruby Best Practices

Pretty-Printer for Ruby Objects (pp)

As I mentioned before, Ruby standard libraries run the gamut from extreme simplicity to deep complexity. I figured we’d kick things off with something in the former category.

If you’re reading this book, you’ve certainly made use of Kernel#p during debugging. This handy method, which calls #inspect on an object and then prints out its result, is invaluable for basic debugging needs. However, reading its output for even relatively modest objects can be daunting:

friends = [ { first_name: "Emily", last_name: "Laskin" },
            { first_name: "Nick",  last_name: "Mauro" },
            { first_name: "Mark",  last_name: "Maxwell" } ]

me = { first_name: "Gregory", last_name: "Brown", friends: friends }

p me # Outputs:

{:first_name=>"Gregory", :last_name=>"Brown", :friends=>[{:first_name=>"Emily",
:last_name=>"Laskin"}, {:first_name=>"Nick", :last_name=>"Mauro"}, {:first_name=
>"Mark", :last_name=>"Maxwell"}]}

We don’t typically write our code this way, because the structure of our objects actually means something to us. Luckily, the pp standard library understands this and provides much nicer human-readable output. The changes to use pp instead of p are fairly simple:

require "pp" friends = [ { first_name: "Emily", last_name: "Laskin" }, { first_name: "Nick", last_name: "Mauro" }, { first_name: "Mark", last_name: "Maxwell" } ] me = { first_name: "Gregory", last_name: "Brown", friends: friends } pp me # Outputs: {:first_name=>"Gregory", :last_name=>"Brown", :friends=> [{:first_name=>"Emily", ...