Rails：活動記錄協會

Question

現在，我對抗AR問題已有兩天了。我知道有一個簡單的解決方案，但我無法弄清楚。

我有兩個模型產品和用戶，應該鏈接在一起。產品應該屬於用戶，用戶應該有許多產品。我沒有設法在我的控制器中設置用戶變量，所以我去了一個habtm關聯。下面是型號：

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，應該是用戶和產品之間的一個一對多的關聯，這工作我出去。 在IRB，我可以這樣做：用的habtm協會

u = User.first 
u.products 

我甚至可以做到這一點viseversa：

p = Product.first 
p.users 

但我不能訪問用戶屬性：

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 

有人能幫我解決這個問題嗎？我究竟做錯了什麼？

非常感謝！你的幫助可以節省我的週末！

編輯：這是我的一個一對多的關係控制器動作：

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

高清顯示 @product = Product.find（PARAMS [：編號]） @images = @ product.product_images respond_to do | format | format.html＃show.html.erb format.json {渲染JSON：@product} 結束 結束

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

如果您有一對多關係，請不要使用has_and_belongs_to_many。創建和維護另一個表會增加太多的複雜性。我的建議是找出爲什麼你不能使一對多關係工作。

你應該能夠使這項工作：

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，複製/粘貼您的控制器，您使用一個一對多的關係碼！

祝你好運

Answer 2

因爲Product有很多users， p.users是一個類似數組的對象。你需要p.users[0].username。

但是，爲什麼你不能使它成爲一個標準的一對多關聯？