0

我无法找出这种关系的错误在哪里：

class Education < ActiveRecord::Base
  attr_accessible :description, :graduation, :student_id, :faculty_id, :department_id

  has_one :faculty
  belongs_to :student
end
#  id          :integer          not null, primary key
#  student_id  :integer
#  faculty_id  :integer
#  description :text
#  graduation  :string(255)

class Faculty < ActiveRecord::Base
  attr_accessible :department_id, :name

  belongs_to :education
  belongs_to :department
end

# == Schema Information
#
# Table name: faculties
#
#  id            :integer          not null, primary key
#  name          :string(255)
#  department_id :integer

为什么我必须添加education_id到faculties表中？每个教育只有一个教师，教师属于许多教育。

>> Education.last.faculty
  Education Load (0.3ms)  SELECT "educations".* FROM "educations" ORDER BY "educations"."id" DESC LIMIT 1
  Faculty Load (0.2ms)  SELECT "faculties".* FROM "faculties" WHERE "faculties"."education_id" = 1 LIMIT 1
SQLite3::SQLException: no such column: faculties.education_id: SELECT  "faculties".* FROM "faculties"  WHERE "faculties"."education_id" = 1 LIMIT 1
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: faculties.education_id: SELECT  "faculties".* FROM "faculties"  WHERE "faculties"."education_id" = 1 LIMIT 1
from /Users/rege/.rvm/gems/ruby-1.9.3-p194@ckdatabase/gems/sqlite3-1.3.6/lib/sqlite3/database.rb:91:in `initialize'
4

2 回答 2

2

无论您在哪一侧放置“belongs_to”，都将始终具有关联对象的 id - 这有点像定义。如果你属于某个东西，你就不属于另一个实例。

如果您希望每个教育只有一个教员，有两种选择：

  • use a one-to-one: when you also want the Faculty to only have one Education
  • use a belongs_to with a one-to-many: when you want each Faculty to have multiple Educations

So you might try this instead:

class Education < ActiveRecord::Base
  attr_accessible :description, :graduation, :student_id, :faculty_id, :department_id

  belongs_to :faculty
  belongs_to :student
end

class Faculty < ActiveRecord::Base
  attr_accessible :department_id, :name

  has_many :education
  belongs_to :department
end
于 2012-11-06T00:26:25.033 回答
1

我认为您的关系有些混乱-官方文档可能会有所帮助。

如果我理解你想要做什么，你需要这样的东西（关于你的教师/教育关系）：

class Education < ActiveRecord::Base
  attr_accessible :description, :graduation, :student_id, :faculty_id, :department_id

  belongs_to :faculty # foreign key - faculty_id
  belongs_to :student
end
#  id          :integer          not null, primary key
#  student_id  :integer
#  faculty_id  :integer
#  description :text
#  graduation  :string(255)

class Faculty < ActiveRecord::Base
  attr_accessible :department_id, :name

  has_many :educations
  belongs_to :department
end
于 2012-11-06T00:25:38.043 回答