Rails 4 has_many 通过 - 无法修改关联

Question

我有一个 DayItem 模型，它有一个包含许多研讨会的 SchoolProgram。

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 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出现以下异常。

ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection in Etm::DayItemsController#update

Cannot modify association 'DayItem#seminars' because the source reflection class 'Seminar' is associated to 'SchoolProgram' via :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创建了循环引用。它在 DayItem 中的 has_many 中声明，然后在 SchoolProgram 中声明为 has_one，SchoolProgram 本身属于父 class DayItem。请尝试对我们的 DayItem 模型进行以下更改。其他模型保持原样，让我知道进展如何。

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

  accepts_nested_attributes_for :school_program
end

Rails 4 has_many 通过 - 无法修改关联

Rails 4 has_many through - Cannot modify association

nested

ruby-on-rails

nested-forms

cocoon-gem

关系中的循环引用（源反射）