How does Ruby return two values?

Question

Whenever I swap values in an array, I make sure I stored one of the values in a reference variable. But I found that Ruby can return two values as well as automatically swap two values. For example,

array = [1, 3, 5 , 6 ,7] array[0], array[1] = array[1] , array[0] #=> [3, 1]  

I was wondering how Ruby does this.

Answer 1

Unlike other languages, the return value of any method call in Ruby is always an object. This is possible because, like everything in Ruby, nil itself is an object.

There's three basic patterns you'll see. Returning no particular value:

def nothing end  nothing # => nil 

Returning a singular value:

def single   1 end  x = single # => 1 

This is in line with what you'd expect from other programming languages.

Things get a bit different when dealing with multiple return values. These need to be specified explicitly:

def multiple   return 1, 2 end  x = multiple # => [ 1, 2 ] x # => [ 1, 2 ] 

When making a call that returns multiple values, you can break them out into independent variables:

x, y = multiple # => [ 1, 2 ] x # => 1 y # => 2 

This strategy also works for the sorts of substitution you're talking about:

a, b = 1, 2 # => [1, 2] a, b = b, a # => [2, 1] a # => 2 b # => 1