What does Post.all.map(&:id) mean? [duplicate]

Answer 1

& means that you are passing a block

Post.all is the receiver of the method .map, and its block is being passed on

Post.all.map { |item| # do something }

http://ruby-doc.org/core-1.9.3/Enumerable.html#method-i-map

It iterates over the array and create a lambda with symbol#to_proc

http://ruby-doc.org/core-1.9.3/Symbol.html#method-i-to_proc