What does map(&:name) mean in Ruby?

Question

I found this code in a RailsCast:

def tag_names
  @tag_names || tags.map(&:name).join(\' \')
end

What does the (&:name)

Answer 1

Another cool shorthand, unknown to many, is

array.each(&method(:foo))

which is a shorthand for

array.each { |element| foo(element) }

By calling method(:foo) we took a Method object from self that represents its foo method, and used the & to signify that it has a to_proc method that converts it into a Proc.

This is very useful when you want to do things point-free style. An example is to check if there is any string in an array that is equal to the string "foo". There is the conventional way:

["bar", "baz", "foo"].any? { |str| str == "foo" }

And there is the point-free way:

["bar", "baz", "foo"].any?(&"foo".method(:==))

The preferred way should be the most readable one.