查找对象是否在Ruby中的数组中？

Question

So I thought this would be pretty basic but I'm having no luck in finding out whether an object with the same attributes as one within an array is in fact in the array. The below code returns false:

hand = [Card.new(:ace)]
puts("#{hand.include?(Card.new(:ace))}")

yet I can't see how I can check if the card in the hand array has the same contents of the card I provide in the include? argument.

Answer 1

assuming

class Card
  attr_reader :card

  def initialize(card)
    @card = card
  end
end

you can use:

hand.find { |c| c.card == :ace }

find returns either first matching element or nil

Answer 2

So the proper way to ensure object equality is to implement #== and #hash

class Card
  attr_accessor :card

  def initialize(card)
    @card = card
  end

  def ==(other)
    other.class == self.class && other.card == @card
  end

  alias_method :eql?, :==

  def hash
    @card.to_s.hash
  end
end

p Card.new(:ace) == Card.new(:ace)
#=> true

Answer 3

You would need to add a method to measure equality between cards of the card class. Your class may look like this:

class Card

  attr_reader :value

  def initialize(v)
    @value = v
  end

  def ==(other_card)
    @value == other_card.value
  end
end