Rails has_many 关联 [英] Rails has_many associations

问题描述

考虑以下模型，如何只选择用户拥有的学生笔记?另外，模型看起来还好吗?

Considering the following models, how can I select only the notes of students owned by a user? Also, do the models look ok?

class Student < ActiveRecord::Base
    has_many :student_notes
    has_many :notes, :through => :student_notes

    has_many :relationships
    has_many :users, :through => :relationships
end

class Note < ActiveRecord::Base
    has_many :student_notes
    has_many :students, :through => :student_notes
end

class StudentNote < ActiveRecord::Base
    belongs_to :student
    belongs_to :note
end

class User < ActiveRecord::Base
    has_many :relationships
    has_many :students, :through => :relationships
end

class Relationship < ActiveRecord::Base
  belongs_to :student
  belongs_to :user
end

提前致谢！

推荐答案

你可以简化你的模型，去掉 StudentNote 和 Relationship 并使用 has_and_belongs_to_many代码> 关联.

You could simplify your models cutting off StudentNoteand Relationship and using the has_and_belongs_to_many association instead.

要仅选择用户拥有的学生笔记，您可以添加 has_many :notes, :through =>;:students 到您的 User 模型

To select only the notes of students owned by a user, you could add has_many :notes, :through => :students to your User model

您的模型应如下所示:

class Student < ActiveRecord::Base
    has_and_belongs_to_many :notes
    has_and_belongs_to_many :users
end

class Note < ActiveRecord::Base
    has_and_belongs_to_many :students
end

class User < ActiveRecord::Base
    has_and_belongs_to_many :students
    has_many :notes, :through => :students
end

您可以通过这种方式选择用户拥有的学生的笔记:

And you could select the notes of students owned by a user this way:

some_user.notes

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