ruby-on-rails - Ruby on Rails 4.2` 上的未定义方法

Question

我有 4 个类，Terminal belongs_to Port，Ports belongs to_Country 和 Countries belongs_to Region。

class Region < ActiveRecord::Base
    has_many :countries
end  

class Country < ActiveRecord::Base
  belongs_to :region
  has_many :ports
end

class Port < ActiveRecord::Base
  belongs_to :country
  has_many :terminals
end

class Terminal < ActiveRecord::Base
  belongs_to :port
end

我正在尝试运行以下代码:

class TerminalsController < ApplicationController
    def index    
        @country = Country.find_by name: 'Pakistan'
        @terminals = @country.ports.terminals
    end
end

我收到以下错误: 未定义的方法 terminals对于 #<Port::ActiveRecord_Associations_CollectionProxy:0x007fde543e75d0>

我得到以下错误:

未定义的方法 ports对于 <Country::ActiveRecord_Relation:0x007fde57657b00>

Answer 1

@country.ports 返回端口数组，不返回终端数组。您应该声明 has_many :through 与 Country 模型的关系。

class Country < ActiveRecord::Base
  belongs_to :region
  has_many :ports
  has_many :terminals, through: :ports
end

比 Controller ，

class TerminalsController < ApplicationController
    def index    
        @country = Country.find_by name: 'Pakistan'
        @terminals = @country.terminals # Don't need intermediate ports
    end
end

另请参阅:

• Rails Guide