Sort a list of objects using their attributes in Ruby

Question

I have a list of structures Fruitcalled basket. Each structure Fruithas name(a string) and calories(an integer). I would like to sort basketso that:

• First displayed Fruitwith the highest calories. For example, a fruit with 500 calories appears in front of a fruit with 400 calories.

• If two Fruithave equal calories, then Fruitwhose namecomes first in alphabetical order, first, ignoring case. For example, given two fruits with the same calories, one of them, called “banana,” appears before it is called “Citrus.”

Definition Fruitis not something that I control, so I would prefer a solution that should not mix anything with Fruitor modify it. Is it possible?

Answer 1

Easy solution

basket.sort_by { |f| [-f.calories, f.name] }

Of course, if this is the canonical sorting order for fruits, then it must be determined using the method <=>and with the module Comparablemixed inFruit

Answer 2

Suppose your basket is an array or its subclass.

Quick way

Enumerable.sort_by

Gareth, Enumerable ( Array) sort_by, . , .

# -f.calories to sort descending
# name.downcase to do a case-insensitive sort
basket = basket.sort_by { |f| [-f.calories, f.name.downcase] }

Perl

Array.sort

Perl, <= > . . ! , . , , , , . - , Ruby StackOverflow.

baseket.sort! { |a,b|
  if a.calories == b.calories
    a.name.downcase <=> b.name.downcase
  else
    # Reverse the result to sort highest first.
    -(a.calories <=> b.calories)
  end
}

Answer 3

. Array#sort (API doc). , -1, 0 1, Fruit, , , .

Answer 4

, , , .

Spaceship-Operator (<=>) 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

:

list_of_fruits.sort

(==, <, >) , , if (apple < banana) (. )

<=> Is returned for a refund -1if selfless other, +1if otherless, and 0if the two objects are equal.