使用强参数匹配 collection_select 输出答案

【问题标题】：Matching up collection_select output with strong parameters使用强参数匹配 collection_select 输出
【发布时间】：2014-11-10 23:01:24
【问题描述】：

在 Rails 控制台中并使用以下模型，我将成绩 K、1 和 2 连接到其编辑表单具有此选择字段的学校：

如您所见，该关联正确地选择了该字段中的 3 个项目，但如果我单击选择/取消选择成绩，这些更改不会被保存。

以下是模型：

# app/models/school.rb
class School < ActiveRecord::Base
  has_many :grades_schools, inverse_of: :school
  has_many :grades, through: :grades_schools
  accepts_nested_attributes_for :grades_schools, allow_destroy: true
end

# app/models/grades_school.rb
class GradesSchool < ActiveRecord::Base
  belongs_to :school
  belongs_to :grade
end

# app/models/grade.rb
class Grade < ActiveRecord::Base
  has_many :grades_schools, inverse_of: :grade
  has_many :schools, through: :grades_schools
end

表格如下所示：

# app/views/schools/_form.html.haml
= form_for(@school) do |f|
  / <snip> other fields
  = collection_select(:school, :grade_ids, @all_grades, :id, :name, {:selected => @school.grade_ids, include_hidden: false}, {:multiple => true})
  / <snip> other fields + submit button

控制器看起来像这样：

# app/controllers/schools_controller.rb
class SchoolsController < ApplicationController
  before_action :set_school, only: [:show, :edit, :update]

  def index
    @schools = School.all
  end

  def show
  end

  def new
    @school = School.new
    @all_grades = Grade.all
    @grades_schools = @school.grades_schools.build
  end

  def edit
    @all_grades = Grade.all
    @grades_schools = @school.grades_schools.build
  end

  def create
    @school = School.new(school_params)

    respond_to do |format|
      if @school.save
        format.html { redirect_to @school, notice: 'School was successfully created.' }
        format.json { render :show, status: :created, location: @school }
      else
        format.html { render :new }
        format.json { render json: @school.errors, status: :unprocessable_entity }
      end
    end
  end

  def update
    respond_to do |format|
      if @school.update(school_params)
        format.html { redirect_to @school, notice: 'School was successfully updated.' }
        format.json { render :show, status: :ok, location: @school }
      else
        format.html { render :edit }
        format.json { render json: @school.errors, status: :unprocessable_entity }
      end
    end
  end

  private
    def set_school
      @school = School.find(params[:id])
    end

    def school_params
      params.require(:school).permit(:name, :date, :school_id, grades_attributes: [:id])
    end
end

我感觉问题的症结在于collection_select 生成的参数与强参数之间的不匹配。其中一项或两项可能不正确，但我一生都无法在网上找到示例代码来告诉我我做错了什么。

在尝试了很多失败的变体之后，我束手无策！提前感谢您的帮助！

【问题讨论】：

标签： ruby-on-rails has-and-belongs-to-many form-for strong-parameters collection-select

【解决方案1】：

废话。我可以发誓我以前试过这个，但肯定是在表单中使用fields_for 而不是collection_select 时。解决办法：

def school_params
  params.require(:school).permit(:name, :date, :school_id, grades_attributes: [:id])
end

变成

def school_params
  params.require(:school).permit(:name, :date, :school_id, grade_ids: [])
end

我仍然很好奇使用 fields_for @grades_schools 时它会如何工作，但必须将调查留到另一天......

【讨论】：