What does “temps.each(&:valid?)” mean in Ruby? [duplicate]

Answer 1

&:symbol is a shorthand for symbol to proc.

Here's a good blog post on it. http://blog.hasmanythrough.com/2006/3/7/symbol-to-proc-shorthand

Answer 2

The & is called the to_proc operator. It expands the symbol (:valid?) into a Proc. So your example is equivalent to:

temps.each { |t| t.valid? }