One thing I love about ruby is that mostly it is a very readable language (which is great for self-documenting code)

However, inspired by this question: http://stackoverflow.com/questions/609612/ruby-code-explained and the description of how ||= works in ruby, I was thinking about the ruby idioms I don't use, as frankly, I don't fully grok them.

So my question is, similar to the example from the referenced question, what common, but not obvious, ruby idioms do I need to be aware of to be a truly proficient ruby programmer?

By the way, from the referenced question

a ||= b

is equivalent to

if a == nil || a == false
  a = b
end

(Thanks to Ian Terrell for the correction)

Edit: It turns out this point is not totally uncontroversial. The correct expansion is in fact

(a || (a = (b)))

See these links for why:

• http://DABlog.RubyPAL.Com/2008/3/25/a-short-circuit-edge-case/
• http://DABlog.RubyPAL.Com/2008/3/26/short-circuit-post-correction/
• http://ProcNew.Com/ruby-short-circuit-edge-case-response.html

Thanks to Jörg W Mittag for pointing this out.