MongoMapper + Rails 协会不起作用

Question

我想要一个与两个用户关联的 ECardMatch，并且能够通过这样的关联创建 @user.ecard_matches.new 等...

我能够执行如下操作

user = User.new
user.ecard_matches

：返回一个 [] 空数组

但我不能这样做

em = EcardMatch.new
user.ecard_matches << em

错误：

NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.include?

或 user.ecard_matches.new

错误：

NoMethodError: undefined method `new' for []:Array

模型中的关联可能有问题。我是 Rails 和 mongodb 的新手，所以也许这种用法是不好的做法...

用户类：

class User
  include MongoMapper::Document

  attr_accessor :password

  key :name, String
  key :perika, Integer
  key :digest_password, String

  many :ecard_matches
end

EcardMatch 类：

class EcardMatch
  include MongoMapper::Document

  key :wager, Integer
  key :turn, Integer
  key :first_user_score, Integer
  key :second_user_score, Integer

  belongs_to :first_user, class_name: "User"
  belongs_to :second_user, class_name: "User"

end

Answer 1

user = User.new 
user.ecard_matches << EcardMatch.new(:prop1=> '....', :prop1=> '....', ...)
user.ecard_matches << EcardMatch.new(:prop1=> '....', :prop2=> '....', ....)
user.save

这个例子有帮助吗？