Ruby on rails Rails中多对多关联的值无法保存在数据库中。

我有用户和角色表，它们具有多对多关联。我的数据库有用户、角色和角色用户表。基本上我想把用户的角色保存在role_users表中，这个表基本上是用户和角色的连接表。我从roles表中获取用户页面上的用户角色，并希望将它们保存在role\u users表中。但我无法在role_users表中保存用户的角色。我已经在用户的“createcontroller”中编写了代码来将数据保存在role_users表中，但这并没有发生

用户\u控制器.rb

class Admin::UsersController < Admin::BaseController
  before_filter :find_user, :only => [:show, :edit, :update, :destroy]
  def index
    @users = User.all( :order => :email ) 
    @roles = Role.all
  end

  def show
  end

  def new
    @user = User.new
  end

  def create
    is_admin = params[:user].delete(:is_admin) == "1"
    @user = User.new(params[:user])
    **@user_role = RoleUser.new({:user_id => @user.id, :role_id => params[:role_user]})**
    #@user_role.role_id = params[:role_id]
    #@user_role.user_id = current_user.id
    @user_role.save

    @user.is_admin = is_admin
  if @user.save
    flash[:notice] = "User has been created."
    redirect_to admin_users_path
  else
    flash[:alert] = "User has not been created."
    render :action => :new
  end
 end

  def edit
  end

  def update
    if params[:user][:password].empty?
      params[:user].delete(:password)
    end

    set_admin
    if @user.update_attributes(params[:user])
      flash[:notice] = "User has been updated."
      redirect_to admin_users_path
    else
      flash[:alert] = "User has not been updated."
      render :action => :new
    end
  end

  def destroy
    if @user == current_user
      flash[:alert] = "You cannot delete yourself!"
    else
      @user.destroy 
      flash[:notice] = "User has been deleted."
    end
    redirect_to admin_users_path
  end

  private

  def find_user
    @user = User.find(params[:id])
  end

  def set_admin
    is_admin = params[:user].delete(:is_admin) == "1"
    @user.is_admin = true
  end
end

# encoding: UTF-8
# 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 => 20130601093644) do




  create_table "role_users", :force => true do |t|
    t.integer  "role_id"
    t.integer  "user_id"
    t.datetime "created_at", :null => false
    t.datetime "updated_at", :null => false
  end

  create_table "roles", :force => true do |t|
    t.string   "name"
    t.datetime "created_at", :null => false
    t.datetime "updated_at", :null => false
  end

  create_table "team_users", :force => true do |t|
    t.integer  "team_id"
    t.integer  "user_id"
    t.integer  "team_lead_id"
    t.datetime "created_at",   :null => false
    t.datetime "updated_at",   :null => false
  end

  create_table "teams", :force => true do |t|
    t.string   "name"
    t.datetime "created_at",   :null => false
    t.datetime "updated_at",   :null => false
    t.integer  "team_lead_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.boolean  "is_admin"
    t.string   "username"
    t.string   "first_name"
    t.string   "last_name"
    t.string   "contact_no"
    t.date     "birth_date"
    t.boolean  "is_active"
    t.date     "joining_date"
    t.string   "avatar_url"
    t.boolean  "is_hr"
    t.boolean  "is_manager"
    t.string   "designation"
    t.string   "user_code"
    t.string   "user_role"
  end

  add_index "users", ["email"], :name => "index_users_on_email", :unique => true
  add_index "users", ["reset_password_token"], :name => "index_users_on_reset_password_token", :unique => true

end

class User < ActiveRecord::Base
 has_many :roles,  through: :role_users
 has_many :role_users
  # Include default devise modules. Others available are:
  # :token_authenticatable, :confirmable,
  # :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  # Setup accessible (or protected) attributes for your model
  attr_accessible :username, :email, :password, :password_confirmation, 
  :remember_me, :first_name, :last_name, :is_admin, :contact_no, :birth_date,
   :joining_date, :is_active, :is_hr, :is_manager, :user_code, :designation
  # attr_accessible :title, :body
end

class RoleUser < ActiveRecord::Base
  belongs_to :user
  belongs_to :role
  attr_accessible :role_id, :user_id
end

class Role < ActiveRecord::Base
  attr_accessible :name
  has_many :users,  through: :role_users
  has_many :role_users

end

\u form.html.erb（用于创建新用户）

---

但是，数据不会保存在db中。

在创建

角色扮演者时，
用户实例中还没有id

def create
  is_admin = params[:user].delete(:is_admin) == "1"
  @user = User.new(params[:user])

  # @user is not saved here and has no id

  **@user_role = RoleUser.new({:user_id => @user.id, :role_id => params[:role_user]})**

  @user_role.save

  # based on your validations, it's likely that this @user_role.save is returning false

在与星星的连线上，@user已经生成，但没有保存。保存
User
后，尝试构建
RoleUser
实例

尝试在以下行后保存
角色扮演者
：
如果@user.save
在创建
角色扮演者
时，您的
用户
实例中还没有id

def create
  is_admin = params[:user].delete(:is_admin) == "1"
  @user = User.new(params[:user])

  # @user is not saved here and has no id

  **@user_role = RoleUser.new({:user_id => @user.id, :role_id => params[:role_user]})**

  @user_role.save

  # based on your validations, it's likely that this @user_role.save is returning false

在与星星的连线上，@user已经生成，但没有保存。保存
User
后，尝试构建
RoleUser
实例

请尝试在这一行之后保存您的
RoleUser
：if@user.save
hi@GSP，谢谢您的回复。根据您的建议，我们可以在角色用户表中保存用户id。但仍然没有保存角色_id，它在表中显示nil值。你知道吗？看起来你在控制器中引用了
role\u user
作为你的参数，但它的形式不是
role\u id
？所以它看起来像：
@user\u role=RoleUser.new（{:user\u id=>@user.id，：role\u id=>params[:role\u id]}）
hi@GSP，谢谢你的回复。根据您的建议，我们可以在角色用户表中保存用户id。但仍然没有保存角色_id，它在表中显示nil值。你知道吗？看起来你在控制器中引用了
role\u user
作为你的参数，但它的形式不是
role\u id
？所以它看起来像：
@user\u role=RoleUser.new（{:user\u id=>@user.id，：role\u id=>params[：role\u id]}）
def create
  is_admin = params[:user].delete(:is_admin) == "1"
  @user = User.new(params[:user])

  # @user is not saved here and has no id

  **@user_role = RoleUser.new({:user_id => @user.id, :role_id => params[:role_user]})**

  @user_role.save

  # based on your validations, it's likely that this @user_role.save is returning false