Rails 4 has_many through - 无法修改关联

Question

我有DayItem模型，它有一个SchoolProgram，有许多研讨会。

class DayItem < ActiveRecord::Base
  has_one :school_program, dependent: :destroy
  has_many :seminars, through: :school_program

  accepts_nested_attributes_for :school_program
  accepts_nested_attributes_for :seminars, reject_if: :all_blank
end

class SchoolProgram < ActiveRecord::Base
  belongs_to :day_item
  has_many :seminars, dependent: :destroy

  accepts_nested_attributes_for :seminars, allow_destroy: true, reject_if: :all_blank
end

class Seminar < ActiveRecord::Base
  belongs_to :school_program
end

我正在使用cocoon gem作为动态嵌套表单，如下所示。

_form.html.haml：

= simple_form_for [@day, @day_item] do |f|
  = f.input :start_time
  = f.simple_fields_for :school_program do |form|
    = form.input :school
    = form.simple_fields_for :seminars do |seminar|
      = render 'seminar_fields', :f => seminar, :parent => form
    .links
      = link_to_add_association 'add seminar', form, :seminars

_seminar_fields.html.haml：

.nested-fields.well.well-compact
  .form-inline
    = f.input :name
    = link_to_remove_association "remove seminar", f

但是当我尝试添加研讨会时，我会遇到异常。

  

ActiveEcord :: HasManyThroughCantAssociateThroughHasOneOrManyReflection在Etm :: DayItemsController＃update

     

无法修改关联'DayItem＃seminars'，因为源反射类'Seminar'通过以下方式与'SchoolProgram'相关联：has_many。

感谢任何帮助。

Answer 1

关系中的循环引用（源反射）

这里可能存在多个问题，但第一个应该解决的问题是您与研讨会的关系会创建一个循环引用。它在DayItem中的has_many中声明，然后在SchoolProgram上声明为has_one，它本身属于父类DayItem。请尝试以下更改我们的DayItem模型。保留其他型号，让我知道它是怎么回事。

class DayItem < ActiveRecord::Base
  has_one :school_program, dependent: :destroy

  accepts_nested_attributes_for :school_program
end