实例变量找不到 id答案

【问题标题】：instance variable can't find id实例变量找不到 id
【发布时间】：2013-03-12 00:43:51
【问题描述】：

我正在创建一个画廊应用程序。我需要在类的索引操作上引用实例变量@image。但是，当我在 Class 中声明它时，它会导致 Couldn't find Image without an ID。如何解决此错误。

class Admin::ImagesController < ApplicationController
    before_filter :get_album, :only => [:show, :index, :destroy]
    def index
        @images = Image.all
        @image = Image.find(params[:image_id])
    end
    def new
        @album = Album.find(params[:album_id])
        @image = Image.new(params[:image_id])
    end
    def create
        @image = Image.new(params[:image])
        if @image.save
            flash[:notice] = "Successfully added image!"
            redirect_to [:admin, :albums]
        else
            render :action => 'new'
        end
    end
    def show
        @image = Image.find(params[:id])
    end
    def destroy
        @image = Image.find(params[:image_id])
        @image.destroy
        redirect_to admin_albums_path
    end
    private
    def get_album
        @album = Album.find(params[:album_id])
    end

end

Index.html.erb

<% @images.each do |image|%>
    <%= image.title %>
    <%= image.description %>
    <%= image.image_name %>
    <%= button_to "Delete", @image, :method => :delete, :style => "display: block;" %>
    <%= debug @image %>
<% end %>

架构

# This file is auto-generated from the current state of the database. Instead
# of editing this file, please use the migrations feature of Active Record to
# incrementally modify your database, and then regenerate this schema definition.
#
# Note that this schema.rb definition is the authoritative source for your
# database schema. If you need to create the application database on another
# system, you should be using db:schema:load, not running all the migrations
# from scratch. The latter is a flawed and unsustainable approach (the more migrations
# you'll amass, the slower it'll run and the greater likelihood for issues).
#
# It's strongly recommended to check this file into your version control system.

ActiveRecord::Schema.define(:version => 20130312005119) do

  create_table "albums", :force => true do |t|
    t.string   "title",       :null => false
    t.text     "description"
    t.date     "date"
    t.datetime "created_at",  :null => false
    t.datetime "updated_at",  :null => false
  end

  create_table "images", :force => true do |t|
    t.string   "title"
    t.string   "description"
    t.string   "image_name"
    t.datetime "date"
    t.integer  "album_id"
    t.integer  "image_id"
  end

  create_table "users", :force => true do |t|
    t.string   "email"
    t.string   "password_digest"
    t.datetime "created_at",      :null => false
    t.datetime "updated_at",      :null => false
  end

end

路线

Admin::Application.routes.draw do
  get "albums/index"

  get "dashboard/index"

  namespace :admin, :shallow => true do
    root :to => "dashboard#index"
    resources :dashboard
    resources :albums do
      resources :images
     end
    get "admin/album"
    end
    get "logout" => "sessions#destroy", :as => "logout"
  get "login" => "sessions#new", :as => "login"
  get "signup" => "users#new", :as => "signup"
    # resources :users
  resources :basic
    root :to => "basic#index"

【问题讨论】：

显示该错误是因为params[:image_id] 为零，您能否向我们显示参数（请参阅服务器日志）
如果您访问的是params[:image_id]，您需要确保image_id 存在。因此，例如，?image_id=1 应该附加到您的图片 URL 中。
它在模式中。我应该在“图像创建表单”上添加 hidden_field_tag 吗？
顺便说一句，当我做@image = Image.find(params[:id])时出现同样的错误@
在控制台中，输入rake routes。将输出粘贴到原始提交中。

标签： ruby-on-rails ruby-on-rails-3 rails-activerecord

【解决方案1】：

如果你想在 DB 中不存在 Image 的情况下使用它，那么你必须做 find_by_id

@image = Image.find_by_id(params[:image_id])

这将返回 Nil 而不是错误。

【讨论】：

【解决方案2】：

为什么要在 Image 模型中使用 image_id 列。创建模型时会自动生成 id 列。从您的 Image 模型中删除 image_id 并在您的图像控制器索引中使用

@images = Image.all

【讨论】：