Ruby 私有实例变量，但有例外

Question

我正在用红宝石制作纸牌游戏。

我有 Game 类，它有一个 Player 对象数组。

 array_of_players = Array[
  Player.new("Ben"),
  Player.new("Adam"),
  Player.new("Peter"),
  Player.new("Fred"),
 ]
 my_game = Game.new(array_of_players)

 puts my_game.players[2].name #=> Peter

每个玩家也可以访问游戏，这样他们就可以访问游戏的重要部分，就像

self.game.last_card_dealt

每个玩家也有卡牌（Player.cards）一样，我想确保玩家不能访问彼此的卡牌。但是，游戏确实需要访问卡牌，所以我认为使用 private 不合适，而且玩家需要访问彼此的一些信息，所以我不认为我想要这样要么是私有...

基本上，我希望这些能够工作。

self.cards #where self is a Player object
self.players[0].cards #where self is the Game
self.game.players[0].name #where self is a Player object

这会失败：

self.hand.players[0].cards  #=> Nice try sucker! Cheating is for losers.

如何处理像这样的更复杂的权限？ 谢谢。

Answer 1

这比我的其他答案更实用，并使用 Game 对象作为游戏本身所有信息（玩家、卡牌等）的委托。请注意，您仍然必须相信呼叫者能够自行传递，但说真的，您在哪里划清界限呢？

class Player
  attr_reader :name

  def initialize(name)
    @name = name
  end
end

class Cards
  attr_accessor :cards
end

class Game
  attr_reader :name, :players

  def initialize(players)
    @name = "Game Master"
    @hands = []
    @players = players.each do |p|
      puts "Added %s to game." % p.name
      @hands << {:player => p, :cards => Cards.new}
    end
  end

  def view_hand(player, caller)
    @hands.each do |hand|
      if hand[:player] == player
        if hand[:player] == caller or caller == self
          puts "%s: You can access all these cards: %s" % [caller.name, hand[:cards]]
        else
          # Do something to only display limited cards depending on this caller's view capabilities
          puts "%s: You can only access the cards I will let you see: %s" % [caller.name, hand[:cards]]
        end
      end
    end
  end

  def my_cards(player)
    @hands.each do |hand|
      puts "%s's cards: %s" % [player.name, hand[:cards]] if hand[:player] == player
    end
  end

end

g = Game.new([Player.new('Bob'), Player.new('Ben')])

puts "\nCalling each Player's cards as each Player:\n\n"
g.players.each do |gp|
  g.players.each do |p|
    g.view_hand(gp, p)
  end
end

puts "\nCalling each Player's cards as Game:\n\n"
g.players.each do |p|
  g.view_hand(p, g)
end

puts "\nEach Player calls for their own cards:\n\n"
g.players.each do |p|
  g.my_cards(p)
end

输出：

    Added Bob to game.
    Added Ben to game.

    Calling each Player's cards as each Player:

    Bob: You can access all these cards: #<Cards:0x100121c58>
    Ben: You can only access the cards I will let you see: #<Cards:0x100121c58>
    Bob: You can only access the cards I will let you see: #<Cards:0x100121bb8>
    Ben: You can access all these cards: #<Cards:0x100121bb8>

    Calling each Player's cards as Game:

    Game Master: You can access all these cards: #<Cards:0x100121c58>
    Game Master: You can access all these cards: #<Cards:0x100121bb8>

    Each Player calls for their own cards:

    Bob's cards: #<Cards:0x100121c58>
    Ben's cards: #<Cards:0x100121bb8>

Answer 2

将 Game.player 保持私有以禁止玩家通过数组访问其他玩家。

例如，当 self 是玩家时，self.game.players[0].name 有点愚蠢。

也许您想要一个仅返回玩家姓名数组的公共 Game.player_names 方法？

最重要的是，您可以创建一个公共 Players.opponents 方法。

示例

Game.player_names

class Game
  # ...
  def player_names
    self.players.collect { |p| p.name }
  end

  private
  # private game methods
end

Player.opponents

class Player
  # ...
  def opponents(i=nil)
    return i.nil? ? self.game.player_names : self.game.player_names[i]
  end
end

Answer 3

这玩起来很有趣。我不确定这是否是最好的答案，但它确实有效。关键是将调用对象传递给 Player.cards(obj)，并检查它是否是 Player 本身或 Game 类型，两者都具有合法访问权限。

class Player
  attr_accessor :name, :game
  attr_writer :cards

  def initialize(name)
    @name = name
    @game = nil
    @cards = nil
  end

  def cards(caller)
    puts "%s cards called by %s." % [self, caller]
    if caller.kind_of?(Game) or caller == self
      puts "Here's your cards %s." % @cards
    else
      puts "Nice try sucker!  Cheating is for losers."
    end
  end
end

class Cards
  def initialize
    @cards = [1, 2, 3]
  end
end

class Game
  attr_reader :players

  def initialize(players)
    @players = players.each do |p|
      puts "Added %s to game." % p.name
      p.game = self
      p.cards = Cards.new
    end
  end
end

g = Game.new([Player.new('Bob'), Player.new('Ben')])

puts "\nCalling each Player's cards as each Player:\n\n"
g.players.each do |gp|
  g.players.each do |p|
    p.cards(gp)
  end
end

puts "\nCalling each Player's cards as Game:\n\n"
g.players.each do |p|
  p.cards(g)
end

和输出：

    Added Bob to game.
    Added Ben to game.

    Calling each Player's cards as each Player:

    #<Player:0x100122b30> cards called by #<Player:0x100122b30>.
    Here's your cards #<Cards:0x1001229c8>.
    #<Player:0x100122ae0> cards called by #<Player:0x100122b30>.
    Nice try sucker!  Cheating is for losers.
    #<Player:0x100122b30> cards called by #<Player:0x100122ae0>.
    Nice try sucker!  Cheating is for losers.
    #<Player:0x100122ae0> cards called by #<Player:0x100122ae0>.
    Here's your cards #<Cards:0x100122928>.

    Calling each Player's cards as Game:

    #<Player:0x100122b30> cards called by #<Game:0x100122ab8>.
    Here's your cards #<Cards:0x1001229c8>.
    #<Player:0x100122ae0> cards called by #<Game:0x100122ab8>.
    Here's your cards #<Cards:0x100122928>.

Answer 4

感谢您的所有回复。

最后我想我可以给授权对象一个密钥，用于允许它访问方法的核心。

游戏对象具有@auth_object并将其设置为要访问其秘密方法的玩家对象，并且玩家秘密方法检查hand.auth_object是否为self，否则不执行任何操作。然后@auth_object被设置回nil。 @auth_object 有一个 attr_reader 但没有 writer。

那行得通。