一对一的DataMapper关联

Question

我是DataMapper的新手,我正在尝试为以下场景创建模型:

我有很多用户(用户名,密码等),也可以是玩家或裁判,或者两者兼而有(因此不能选择单表继承).基础模型将是:

class User
  include DataMapper::Resource
  property :id, Serial
  # Other user properties go here  
end

class Player
  include DataMapper::Resource
  property :id, Serial
  # Other player properties go here
  # Some kind of association goes here
end

class Referee
  include DataMapper::Resource
  property :id, Serial
  # Other referee properties go here
  # Some kind of association goes here
end

DataMapper.finalize

不过,我不确定添加到播放器和裁判的关联类型.有了belongs_to :user,多个玩家可以与同一个用户相关联,这在我的上下文中没有意义.在RDBMS术语中,我想我想要的是对玩家和裁判员表中的外键的唯一约束.

我如何在DataMapper模型中完成此操作？我是否必须在验证中自行执行检查？

Answer 1

有不同的方法可以做到这一点.这是一个选项:

class User
  include DataMapper::Resource
  property :id, Serial
  # Other properties...
  has 1, :referee, :required => false
  has 1, :player, :required => false
end

class Referee
  include DataMapper::Resource
  # DON'T include "property :id, Serial" here
  # Other properties...
  belongs_to :user, :key => true
end
class Player
  include DataMapper::Resource
  # DON'T include "property :id, Serial" here
  # Other properties...
  belongs_to :user, :key => true
end

对裁判/球员模特的行为如下:

u = User.create(...)
u.referee = Referee.create(...)
u.player = Player.create(...)

u.player.kick_ball() # or whatever you want to call
u.player.homeruns
u.referee.flag_play() # or whatever.

看看这是否有效.我实际上没有测试过,但它应该是好的.