Rails：活动记录协会

Question

我现在已经 2 天以来一直在努力解决 AR 关联的问题。我知道有一个简单的解决方案，但我不知道。

我有两个模型产品和用户，它们应该链接在一起。一个产品应该属于一个用户，一个用户应该有很多产品。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。以下是模型：

用户.rb

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

has_and_belongs_to_many :products

产品.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，用户和产品之间应该存在一对多的关联，这对我来说很有效。 在 IRB 中，我可以这样做：

u = User.first
u.products

有了 habtm 协会，我什至可以做到：

p = Product.first
p.users

但我无法访问用户属性：

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？我做错了什么？

非常感谢！你的帮助将节省我的周末！

编辑：这是我对一对多关系的控制器操作：

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

结束

默认显示 @product = Product.find(params[:id]) @images = @product.product_images respond_to 做 |格式| format.html # show.html.erb format.json { 渲染 json: @product } 结尾 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。我的建议是弄清楚为什么不能使一对多关系起作用。

你应该能够完成这项工作：

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


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

如果不起作用，请复制/粘贴用于一对多关系的控制器代码！

祝你好运

Answer 2

因为Product 有很多users，所以p.users 是一个类数组对象。你需要p.users[0].username。

但是为什么不能让它成为标准的一对多关联呢？