我已经检查了类似问题的其他答案,我想我明白他们的意思,但我不知道如何解决它.

我在尝试删除我网站上的博客中的帖子时收到此错误消息.我已经尝试从Rails控制台获得类似的消息.

ActiveRecord::StatementInvalid in PostsController#destroy
Mysql2::Error: Cannot delete or update a parent row: a foreign key constraint fails (`mysite_development`.`comments`, CONSTRAINT `fk_rails_2fd19c0db7` FOREIGN KEY (`post_id`) REFERENCES `posts` (`id`)): DELETE FROM `posts` WHERE `posts`.`id` = 3

posts_controller.rb

class PostsController < ApplicationController
  before_filter :authenticate, :except => [ :index, :show ]
  before_action :set_post, only: [:show, :edit, :update, :destroy]

  # GET /posts
  # GET /posts.json
  def index
    @posts = Post.all
  end

  # GET /posts/1
  # GET /posts/1.json
  def show
  end

  # GET /posts/new
  def new
    @post = Post.new
  end

  # GET /posts/1/edit
  def edit
  end

  # POST /posts
  # POST /posts.json
  def create
    @post = Post.new(post_params)

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

  # PATCH/PUT /posts/1
  # PATCH/PUT /posts/1.json
  def update
    respond_to do |format|
      if @post.update(post_params)
        format.html { redirect_to @post, notice: 'Post was successfully updated.' }
        format.json { render :show, status: :ok, location: @post }
      else
        format.html { render :edit }
        format.json { render json: @post.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /posts/1
  # DELETE /posts/1.json
  def destroy
    @post.destroy
    respond_to do |format|
      format.html { redirect_to posts_url, notice: 'Post was successfully destroyed.' }
      format.json { head :no_content }

    end

  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_post
      @post = Post.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def post_params
      params.require(:post).permit(:title, :body)
    end
end

edit.html.erb

Editing Post

<%= render 'form' %>

<%= link_to 'Show', @post %> |
<%= link_to 'Back', posts_path %>
<%= link_to 'Delete', @post, method: :delete %>

_form.html.erb

<%= simple_form_for(@post) do |f| %>
  <%= f.error_notification %>

  

    <%= f.input :title %>
    <%= f.input :body %>
  

  

    <%= f.button :submit %>
  
<% end %>

有任何想法吗？

它与您的控制器代码无关.您在架构中添加了一个外部约束数据库,该数据库禁止在有关联记录时删除对象.

在这种情况下,您试图删除Post已Comments附加的.您需要更改架构并更新外键定义,以指示数据库在这种情况下要执行的操作.具体来说,您可能希望删除级联上的关联记录.

从理论上讲,您可以使用模型中的dependent: :destroyRails设置Post来删除Comment级联中的s,但这并不是一个好主意,因为您有一个外键.如果在这种情况下将任务委托给数据库,它会更快更好.