RoR教程Michael Hartl刪除Microposts也刪除用戶

Question

我在嘗試在Hartl的Ruby on Rails教程中實現示例應用程序時遇到了一個奇怪的問題。

當我刪除微柱，將發生以下情況：

1. 的微柱被刪除。
2. 該用戶也被刪除。
3. 指示註冊頁面。

只有第一步應該發生。用戶不應該被刪除。當我刪除微博時，控制檯跟蹤顯示以下內容：

Started DELETE "/microposts/1" for 127.0.0.1 at 2013-07-23 11:35:31 -0400 
Processing by MicropostsController#destroy as HTML 
    Parameters: {"authenticity_token"=>"clfdQ1F/1ewiDnuae9OpVXSZ3S/wtieCrVYNM+Y1838=", "id"=>"1"} 
    User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."remember_token" = 'cUs3NX6FrzU-XnkCbGE4wg' LIMIT 1 
    Micropost Load (1.0ms) SELECT "microposts".* FROM "microposts" WHERE "microposts"."user_id" = 1 AND "microposts"."id" = 1 ORDER BY microposts.created_at DESC LIMIT 1 
    (0.0ms) begin transaction 
    SQL (2.0ms) DELETE FROM "microposts" WHERE "microposts"."id" = ? [["id", 1]] 
    User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = 1 LIMIT 1 
    SQL (1.0ms) DELETE FROM "users" WHERE "users"."id" = ? [["id", 1]] 
    (12.0ms) commit transaction 
Redirected to http://localhost:3000/ 
Completed 302 Found in 27ms (ActiveRecord: 16.0ms) 

我不知道爲什麼DELETE FROM「users」正在發送。

我的application.js文件看起來像這樣：

//= require jquery 
//= require jquery_ujs 
//= require bootstrap 
//= require_tree . 

我的routes.rb看起來是這樣的：

SampleApp::Application.routes.draw do 

    resources :users 
    resources :sessions, only: [:new, :create, :destroy] 
    resources :microposts, only: [:create, :destroy] 

    root :to => 'static_pages#home' 
    match '/signup', to: 'users#new' 
    match '/signin', to: 'sessions#new' 
    match '/signout', to: 'sessions#destroy', via: :delete 
    match '/help', to: 'static_pages#help' 
    match '/about', to: 'static_pages#about' 
    match '/contact', to: 'static_pages#contact' 
end 

而且microposts_controller.rb看起來是這樣的：

class MicropostsController < ApplicationController 

    before_filter :signed_in_user, only: [:create, :destroy] 
    before_filter :correct_user, only: :destroy 

    def create 
    @micropost = current_user.microposts.build(params[:micropost]) 
    if @micropost.save 
     flash[:success] = "Micropost created!" 
     redirect_to root_path 
    else 
     @feed_items = [] 
     render 'static_pages/home' 
    end 
    end 

    def destroy 
    @micropost.destroy 
    redirect_back_or root_path 
    end 

    private 

    def correct_user 
    @micropost = current_user.microposts.find_by_id(params[:id]) 
    redirect_to root_path if @micropost.nil? 
    end 
end 

您可以在上面看到如何執行destroy操作（如教程中指定的那樣）。所以我不確定問題是什麼。

這裏是應用程序/模型/ micropost.rb

class Micropost < ActiveRecord::Base 
    # here we removed :user_id from attr_accessable for security reasons 
    attr_accessible :content 
    belongs_to :user, dependent: :destroy 

    validates :content, presence: true, length: { maximum: 140 } 
    validates :user_id, presence: true 

    default_scope order: 'microposts.created_at DESC' 
end 

欣賞任何幫助。

Answer 1

問題出在您的Micropost型號上。下面的行刪除與Micropost相關的user：

belongs_to :user, dependent: :destroy 

替換符合：

belongs_to :user 

，你不會看到相關的用戶越來越刪除。

請通過對「相關協會」這裏的文檔閱讀：http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

更新：

如果你想刪除屬於用戶的所有微柱，那麼你應該在User.rb添加dependent: :destroy類似如下：

has_many :microposts, dependent: :destroy 

Answer 2

你的Micropost類是說用戶應該被銷燬時，微型ost被belongs_to :user上的dependent: :destroy選項破壞。

從documentation for belongs_to對於:dependent如果設置爲：destroy，則關聯的對象在此對象時被銷燬。

所以，如果你刪除dependent: :destroy你不會得到這個問題。