Rails：活动记录协会

Question

现在，我对抗AR问题已有两天了。我知道有一个简单的解决方案，但我无法弄清楚。

我有两个模型产品和用户，应该链接在一起。产品应该属于用户，用户应该有许多产品。我没有设法在我的控制器中设置用户变量，所以我去了一个habtm关联。下面是型号：

User.rb

class User < ActiveRecord::Base 
# Include default devise modules. Others available are: 
#... 

has_and_belongs_to_many :products 

Product.rb

class Product < ActiveRecord::Base 
has_many :product_images, :dependent => :destroy 
accepts_nested_attributes_for :product_images, :allow_destroy => :true 
has_and_belongs_to_many :users 

products_controller.rb

class ProductsController < ApplicationController 

def index 
@products = Product.search(params[:search]).order(sort_column + ' ' + sort_direction).paginate(:per_page => 10, :page => params[:page]) 

respond_to do |format| 
    format.html # index.html.erb 
    format.json { render json: @products } 
end 
end 

def new 
@user = current_user 
@product = Product.new#@user.products.build(params[:product]) 
@product.product_images.build 
respond_to do |format| 
    format.html # new.html.erb 
    format.json { render json: @product } 
end 
end 

def create 
@user = current_user 
@product = @user.products.build(params[:product])#Product.new(params[:product]) 
    @product.product_images.build 
    @user.products << @product 

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

_form.html.erb

<%= form_for @product, :html => {:multipart => true, :class => 'form-horizontal'} do |f| %> 

schema.rb

.... 
create_table "products_users", :id => false, :force => true do |t| 
t.integer "product_id" 
t.integer "user_id" 
end 
.... 

所以，即使我知道，应该是用户和产品之间的一个一对多的关联，这工作我出去。 在IRB，我可以这样做：用的habtm协会

u = User.first 
u.products 

我甚至可以做到这一点viseversa：

p = Product.first 
p.users 

但我不能访问用户属性：

p.users.username: 

NoMethodError: User Load (2.0ms) SELECT "users".* FROM "users" INNER JOIN "products_users" ON "users"."id" = "products_users"."user_id" WHERE "products_users"."product_id" = 12 

有人能帮我解决这个问题吗？我究竟做错了什么？

非常感谢！你的帮助可以节省我的周末！

编辑：这是我的一个一对多的关系控制器动作：

class ProductsController < ApplicationController 

helper_method :sort_column, :sort_direction 
def index 
@products = Product.search(params[:search]).order(sort_column + ' ' + sort_direction).paginate(:per_page => 10, :page => params[:page]) 

respond_to do |format| 
    format.html # index.html.erb 
    format.json { render json: @products } 
end 

末

高清显示 @product = Product.find（PARAMS [：编号]） @images = @ product.product_images respond_to do | format | format.html＃show.html.erb format.json {渲染JSON：@product} 结束 结束

def new 
@user = current_user 
@product = Product.new#@user.products.build(params[:product]) 
@product.product_images.build 
#3.times { @product.product_images.build } 
respond_to do |format| 
    format.html # new.html.erb 
    format.json { render json: @product } 
end 
end 


def edit 
@product = Product.find(params[:id]) 
    @product.product_images.build 
end 


def create 
@user = current_user 
@product = @user.products.build(params[:product])#Product.new(params[:product]) 
    @product.product_images.build 


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


def update 
@product = Product.find(params[:id]) 

respond_to do |format| 
    if @product.update_attributes(params[:product]) 
    format.html { redirect_to @product, notice: 'Product was successfully updated.' } 
    format.json { head :no_content } 
    else 
    format.html { render action: "edit" } 
    format.json { render json: @product.errors, status: :unprocessable_entity } 
    end 
end 
end 


def destroy 
@product = Product.find(params[:id]) 
@product.destroy 

respond_to do |format| 
    format.html { redirect_to products_url } 
    format.json { head :no_content } 
end 
end 

private 
def sort_column 
Product.column_names.include?(params[:sort]) ? params[:sort] : "created_at" 
# params[:sort] || "created_at" 
end 

def sort_direction 
%w[asc desc].include?(params[:direction]) ? params[:direction] : "asc" 
# params[:direction] || "asc" 
end 
end 

EDIT2：Schema.rb

create_table "products", :force => true do |t| 
t.string "title" 
t.string "description" 
t.string "testimonial" 
t.decimal "credits",  :precision => 3, :scale => 0 
t.datetime "created_at",         :null => false 
t.datetime "updated_at",         :null => false 
t.decimal "age" 
t.string "condition" 
t.string "product_image" 
t.string "image" 
t.integer "user_id" 
end 

create_table "users", :force => true do |t| 
t.string "email",     :default => "", :null => false 
t.string "encrypted_password",  :default => "", :null => false 
t.string "reset_password_token" 
t.datetime "reset_password_sent_at" 
t.datetime "remember_created_at" 
t.integer "sign_in_count",   :default => 0 
t.datetime "current_sign_in_at" 
t.datetime "last_sign_in_at" 
t.string "current_sign_in_ip" 
t.string "last_sign_in_ip" 
t.datetime "created_at",        :null => false 
t.datetime "updated_at",        :null => false 
t.string "username" 
t.integer "product_id" 
end 

Answer 1

如果您有一对多关系，请不要使用has_and_belongs_to_many。创建和维护另一个表会增加太多的复杂性。我的建议是找出为什么你不能使一对多关系工作。

你应该能够使这项工作：

class User < ActiveRecord::Base 
    has_many :products #Plural 
end 


class Product < ActiveRecord::Base 
    belongs_to :user #Singular 
end 

如果它不能正常工作，复制/粘贴您的控制器，您使用一个一对多的关系码！

祝你好运

Answer 2

因为Product有很多users， p.users是一个类似数组的对象。你需要p.users[0].username。

但是，为什么你不能使它成为一个标准的一对多关联？