Question

我正在查看此railscast #17 revised作为使用连接表在两个模型之间创建多对多关系的教程：

class Course < ActiveRecord::Base
has_many :courselocalizations
has_many :courselocations, through: :courselocalizations
end

class Courselocation < ActiveRecord::Base
has_many :courselocalizations
has_many :courses, through: :courselocalizations
end

class Courselocalization < ActiveRecord::Base
belongs_to :course
belongs_to :courselocation
end

如果用户在编辑或创建courselocation时未看到现有course，那么他们创建新courselocation并自动建立关联的最佳方式是什么？< / p>

Answer 1

您可以通过两步流程（我的首选方法）或一步完成此操作。

2步骤： - 创建CourseLocation - 关联CourseLocation和Course。

course_location1 = CourseLocation.create(name: 'location1')
course.course_locations << course_location1

如果您想在一步中执行此操作，可以使用Active Record accepts_nested_attributes_for method，这有点棘手。这是一个good article，但让我们打破这些步骤：

课程需要接受course_localizations的属性
课程本地化需要接受course_location的属性
创建课程时，请传递包含位置属性的本地化属性。

让我们为你的特定情况设置所有这些：

class Course < ActiveRecord::Base
  # attribute subject
  has_many :course_localizations, inverse_of: :course
  has_many :course_locations, through: :course_localizations
  accepts_nested_attributes_for :course_localizations
end

class CourseLocation < ActiveRecord::Base
  # attribute city
  has_many :course_localizations
  has_many :courses, through: :course_localizations
end

class CourseLocalization < ActiveRecord::Base
  belongs_to :course
  belongs_to :course_location
  accepts_nested_attributes_for :course_locations
end

此时你应该可以

course = Course.new(
  subject: "Math",
  course_localizations_attributes: [
    { course_location_attributes: { city: "Los Angeles" } },
    { course_location_attributes: { city: "San Francisco" } }]
)

course.save

Rails：多对多的关系 - 创建和关联新记录

1 个答案: