我正在查看这个 railscast #17 修订为教程,以使用连接表在两个模型之间创建多对多关系:
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course
时看不到现有courselocation
,那么创建新courselocation
并自动进行关联的最佳方式是什么?
您可以通过 2 步过程(我的首选方法)或一步完成此操作。
2步流程: - 创建CourseLocation
- 关联CourseLocation
和Course
。
course_location1 = CourseLocation.create(name: 'location1')
course.course_locations << course_location1
如果您想分一步完成此操作,可以使用活动记录accepts_nested_attributes_for
方法,这有点棘手。 这是一篇关于它的好文章,但让我们分解步骤:
- 课程需要接受属性course_localizations
- 课程本地化需要接受属性course_location
- 创建课程时,传递本地化的属性,其中包含位置的属性。
让我们为您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,您应该能够
course = Course.new(
subject: "Math",
course_localizations_attributes: [
{ course_location_attributes: { city: "Los Angeles" } },
{ course_location_attributes: { city: "San Francisco" } }]
)
course.save