Ruby on rails 使用mongoid在用户模型中嵌入国家

我正在使用Rails 4和Mongoid。我有以下型号：

class Country
  include Mongoid::Document

  field :iso
  field :name

  embedded_in :user
end

class User
  include Mongoid::Document

  field :email
  field :name

  embeds_one :country
end

在“编辑用户”视图中，我想将下拉列表与国家/地区一起放置，以便所选国家/地区将被选择为嵌入在用户记录中。我试着用这样的方法：

<%= f.select :country, Country.all.collect { |c| [c.name, c._id] }, :prompt => 'Please select' %>

任何建议都会有帮助。谢谢

Started POST "/users" for 127.0.0.1 at 2014-03-16 16:31:32 +0200
Processing by Devise::RegistrationsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"UzETkbI3MNGBJQg7IhzI6jD5dQCZrvjU0JAgkReTSak=", "user"=>{"first_name"=>"", "last_name"=>"", "email"=>"", "birth_date"=>"", "gender"=>"", "marital_status"=>"", "city"=>"", "country"=>"5324c9f5416c65a032000000", "password"=>"[FILTERED]", "password_confirmation"=>"[FILTERED]"}, "commit"=>"Sign up"}
Completed 500 Internal Server Error in 4ms

NoMethodError - undefined method `__metadata' for "5324c9f5416c65a032000000":String:
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/proxy.rb:141:in `characterize_one'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/embedded/one.rb:20:in `block in initialize'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/proxy.rb:42:in `init'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/embedded/one.rb:19:in `initialize'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/accessors.rb:44:in `new'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/accessors.rb:44:in `create_relation'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/accessors.rb:26:in `__build__'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/accessors.rb:233:in `block (2 levels) in setter'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/accessors.rb:140:in `without_autobuild'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/relations/accessors.rb:229:in `block in setter'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/attributes/processing.rb:141:in `block in process_relations'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/attributes/processing.rb:136:in `each_pair'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/attributes/processing.rb:136:in `process_relations'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/attributes/processing.rb:122:in `process_pending'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/attributes/processing.rb:29:in `process_attributes'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/document.rb:110:in `block in initialize'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/threaded/lifecycle.rb:84:in `_building'
   () Users/alex/.rvm/gems/ruby-2.1.0/bundler/gems/mongoid-164755a9d038/lib/mongoid/document.rb:104:in `initialize'
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  /Users/alex/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
  /Users/alex/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
  /Users/alex/.rvm/rubies/ruby-2.1.0/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'

---

问题是您没有在用户界面中正确设置国家/地区

尝试将以下内容添加到用户模型中 如果要以普通mongoid方式或使用id设置国家/地区

  def country
    @country ||= Country.where(id: country_id).first
  end

  def country=(obj)
    case obj.class
    when String
      self.country_id = obj
      @country = Country.find(obj)
    when Country
      self.country_id = obj.id
      @country = obj
    end
  end

---

你能分享错误的完整跟踪吗？另外，在表单提交时或呈现编辑视图时，您什么时候会出现错误？我实际上会为此创建一个不同于“country”的属性，因为当您实际尝试以“normal”方式设置国家实例时，这会给您带来麻烦。我编辑了答案，以允许仅通过id或“normal”方式设置国家如果遇到任何错误，请尝试并告诉我。我在我遇到的一个案例中，我使用了类似的方法。get函数中不存在country\u id。为什么不为country_id设置get和set函数，而不去管country？我在set和get中使用

@country

。。要模拟mongoid getter和setter行为。。。因此，如果您使用了

user.country

，您实际上得到的是country对象，而不仅仅是id。。。所以

user.country.where（id:'somevalue'）.exist？

实际上会像任何其他mongoid关系一样工作。所以你甚至不会注意到这个字段有一个自定义的setter和getter。。。它的工作方式与您在country（）中返回实例的方式相同，而不是关系，因此您只能在实例或nil:NilClass上获得未定义的方法“where”。

  def country
    @country ||= Country.where(id: country_id).first
  end

  def country=(obj)
    case obj.class
    when String
      self.country_id = obj
      @country = Country.find(obj)
    when Country
      self.country_id = obj.id
      @country = obj
    end
  end