Overriding Ruby's spaceship operator <=>
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27-09-2019 - |
문제
I am trying to override Ruby's <=> (spaceship) operator to sort apples and oranges so that apples come first sorted by weight, and oranges second, sorted by sweetness. Like so:
module Fruity
attr_accessor :weight, :sweetness
def <=>(other)
# use Array#<=> to compare the attributes
[self.weight, self.sweetness] <=> [other.weight, other.sweetness]
end
include Comparable
end
class Apple
include Fruity
def initialize(w)
self.weight = w
end
end
class Orange
include Fruity
def initialize(s)
self.sweetness = s
end
end
fruits = [Apple.new(2),Orange.new(4),Apple.new(6),Orange.new(9),Apple.new(1),Orange.new(22)]
p fruits
#should work?
p fruits.sort
But this does not work, can someone tell what I am doing wrong here, or a better way to do this?
해결책
Your problem is you are only initializing one of the properties on either side, the other one will still be nil
. nil
isn't handled in the Array#<=>
method, which ends up killing the sort.
There are a few ways to handle the problem first would be something like this
[self.weight.to_i, self.sweetness.to_i] <=> [other.weight.to_i, other.sweetness.to_i]
nil.to_i
gives you 0
, which will let this work.
다른 팁
Probably late, nevertheless...
add the following monkeypatch
class Array
def to_i(default=Float::INFINITY)
self.map do |element|
element.nil? ? default : element.to_i
end
end
end
And change the body of Fruity::<=> to
[self.weight, self.sweetness].to_i <=> [other.weight, other.sweetness].to_i
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