两个模型相互依赖 - 捕获22

Here is my scenario:

这是我的情景:

A model called Course has many CourseCodes. A CourseCode belongs to a Course. A CourseCode can't be created without Course and a Course can't be created without at least one CourseCode.

名为Course的模型有许多CourseCodes。 CourseCode属于一个课程。如果没有课程,则无法创建CourseCode,并且如果没有至少一个CourseCode,则无法创建课程。

class Course < ActiveRecord::Base
  has_many :course_codes
  validate :existence_of_code
private
  def existence_of_code
    unless course_codes.any?
      errors[:course_codes] << "missing course code"
    end
  end
end

class CourseCode < ActiveRecord::Base
  belongs_to :course
  validates_presence_of :course
end

The whole scenario feels a bit like catch 22. Is there a way to create both on the same time? I'm using Rails 3.2

整个场景感觉有点像捕获22.有没有办法在同一时间创建两者?我正在使用Rails 3.2

3 个解决方案

#1

Solved the problem by using accepts_nested_attributes_for.

使用accepts_nested_attributes_for解决了这个问题。

Nested attributes allow you to save attributes on associated records through the parent. By default nested.

嵌套属性允许您通过父级保存关联记录的属性。默认情况下嵌套。

class Course < ActiveRecord::Base
  has_many :course_codes, inverse_of: :course
  validate :existence_of_code

  accepts_nested_attributes_for :course_codes

private
  def existence_of_code
    unless course_codes.any?
      errors[:course_codes] << "missing course code"
    end
  end
end

class CourseCode < ActiveRecord::Base
  belongs_to :course, inverse_of: :course_codes
  validates_presence_of :course
end

Used like this.

像这样使用。

Course.create!({
  course_codes_attributes: [{ code: "TDA123" }],
  # ...
})

#2

-1

Looks good to me. Removing the validates_presence_of :course might make things easier on you, too, as it will tend to get in the way an not add much.

在我看来很好。删除validates_presence_of:course也可能会让事情变得更容易,因为它往往会妨碍不添加更多内容。

When you create a course, do it like this:

创建课程时,请执行以下操作:

Course.create course_codes: [CourseCode.new(...), CourseCode.new(...)]

ActiveRecord will figure things out.

ActiveRecord会解决问题。

#3

-1

You could add an unless to whichever model you would plan to create first. For instance:

您可以添加一个除非您计划首先创建的模型。例如:

class CourseCode < ActiveRecord::Base
  belongs_to :course
  validates_presence_of :course, :unless => lambda { Course.all.empty? }
end

#1