I just want to start by saying I’ve been doing ruby development professionally for about 2 years now and like any ruby programmer, I discovered quite a bit of things that didn’t quite work as expected.

A few weeks ago, I found an interesting post that had a collection of these ‘gotchas’ from El Passion - Ruby Gotchas. I’d like to expand on this post but I highly recommend taking a look at the original article.

and vs && with render/redirect_to

To avoid muliple renders or redirect_tos, you’ll want to return to stop the rest of the code from running.

class DashboardController < ApplicationController
  def index
    render 'template' && return #=> index.html.erb

Make sure to use and return instead of && return because && return will not work due to the operator precedence in the Ruby Language.

class DashboardController < ApplicationController
  def index
    render 'template' and return #=> template.html.erb

single quote vs double quote

The main difference between single quotes and double quotes is that single quotes are for literals and auto-escapes escape characters in strings. Because of this, you can’t use string interpolation with single quotes.

> date = Time.now
=> 2014-04-20 20:27:09 -0400

> 'The current time is #{date}'
=> "The current time is \#{date}"

> "The current time is #{date}"
=> "The current time is 2014-04-20 20:27:09 -0400"

Best practices

This just depends on your personal style, I prefer double-quotes unless your string literal contains " or escape characters you want to suppress.


There used to be a performance difference between ' vs " but if you are using >= 1.9.3 it doesn’t matter.

:+ vs &:+

I wouldn’t really call this a gotcha but just something you might want to know. In inject/reduce you don’t need to turn your symbol into a proc. I think this looks a little better but it also gives you a little performance boost.

> [1, 2, 3, 4].reduce(:+)
=> 10

> [1, 2, 3, 4].reduce(&:+)
=> 10


&:+ (  0.000075)
:+  (  0.000046)


This seems to only work for inject/reduce

> ('a'..'z').map(:upcase)
ArgumentError: wrong number of arguments(1 for 0)

Hopefully there will be more ‘gotchas’ to come shortly.