Rails有许多在belongs_to的关系

Question

在我的Rails应用程序，我有以下型号

class Member < ActiveRecord::Base 
    has_many :trainings 
end 

class Student < ActiveRecord::Base 
    belongs_to :member 
    has_many :trainings #maybe a through relationship here 
end 

class Teacher < ActiveRecord::Base 
    belongs_to :member 
end 

######编辑#################

class Training < ActiveRecord::Base 
    belongs_to :member #only member not student nor teacher 
end 

#############################

现在，我怎么能建立在我的培训学生管理员

class StudentsController < ApplicationController 
    def new 
    @student = Student.new 
    @student.trainings.build #### This is not working 
    end 
end 

感谢

Answer 1

你必须写accepts_nested_attributes_for模型和强大的参数添加他们，如果你使用的是轨道4.就像这样：

class Student < ActiveRecord::Base 
    belongs_to :member 
    has_many :trainings  
    accepts_nested_attributes_for :trainings 
end 

class StudentsController < ApplicationController 
    def new 
    @student = Student.new 
    @student.trainings.build 
    end 

    def create 
    @student = Student.create(student_params) 
    @student.trainings.build(params[:student][:trainings]) 

    redirect_to student_path 
    end 

    #For rails 4 

    def student_params 
    params.require(:student).permit(:id, :name, trainings_attributes: [ :id, :your fields here ]) 
    end 
end 

这里是一个链接，这将有助于你： Rails 4: accepts_nested_attributes_for and mass assignment

Answer 2

如果你已经正确地定义了你的关联，那么你的new控制器动作中的代码就可以工作（我测试了它）。检查并确保您的模型存在，或者您使用了正确的关联名称（也许您的意思是:teachers？）。

应用/模型/ student.rb

class Student < ActiveRecord::Base 
    has_many :trainings 
end 

应用/模型/ training.rb

class Training < ActiveRecord::Base 
    belongs_to :student 
end 

应用程序/控制器/ students_controller.rb

class StudentsController < ApplicationController 
    def new 
    @student = Student.new 
    @student.trainings.build 
    end 
end 

更新：

假设这些都是你的关联是如何定义的，你可以建立的Training一个范围的情况下，像这样：

应用程序/模型/ member.rb

class Member < ActiveRecord::Base 
    has_many :trainings 
end 

app/models/student.rb

class Student < ActiveRecord::Base 
    delegate :trainings, to: :member 
    belongs_to :member 
end 

应用程序/模型/ training.rb

class Training < ActiveRecord::Base 
    belongs_to :member 
end 

应用程序/控制器/ students_controller.rb

class StudentsController < ApplicationController 
    def new 
    @student = Student.new 
    @student.build_member 
    @student.trainings.build 
    end 
end 

希望有所帮助。