Sort a list of objects by using their attributes in Ruby

Question

I have a list of Fruit structs called basket. Each Fruit struct has a name (a string) and a calories (an int

Answer 1

If you need to sort Fruits a lot, you should probably do a little more work up front and make your objects comparable.

For this, you need to implment the Spaceship-Operator (<=>) and include Comparable.

class Fruit
  attr_accessor :name, :color

  def <=>(other)
    # use Array#<=> to compare the attributes
    [self.name.downcase, self.color] <=> [other.name.downcase, other.color]
  end

  include Comparable
end

then you can simply do:

list_of_fruits.sort

Comparable also gives you many other methods (==, <, >) for free, so you can do things like if (apple < banana) (see the documentation for the Comparable Module for more info)

<=>, is specified to return -1 if self is smaller than other, +1 if other is smaller and 0 if both objects are equal.