设计nil的undefined方法'build'：NilClass

Question

我目前参加了Ruby on Rails的在线课程，即时通讯从零开始学习所有的东西，所以请原谅我，如果我在我的问题中不清楚。这里是我的delima，我试图在rails应用程序中的两个模型之间创建一个LINK，这是我迄今为止所做的。但是当我尝试访问localhost3000/business/new时，它返回错误提到它的标题。我得出的结论是，这是因为我使用了“has_one：model”类型的关联，而不是“has_many：model”。我希望有人能在这里指出我正确的方向，因为我花了数小时寻找解决方案。

class BusinessesController < ApplicationController 
    before_action :set_business, only: [:show, :edit, :update, :destroy] 
    //edited for clarity 
    def new 
    @business = current_user.business.build //The line that returns a undefined method for nil class 
    end 

    def edit 
    end 

    def create 
    @business = current_user.business.build(business_params) 

    if @business.save 
     redirect_to @business, notice: 'Business was successfully created.' 
    else 
     render "new" 
    end 
    end 

设计用户模型

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

    has_many :buzzs, dependent: :destroy 
    has_one :business, dependent: :destroy 
end 

商业模式

class Business < ActiveRecord::Base 
    belongs_to :user 
end 

Answer 1

看看这个http://guides.rubyonrails.org/association_basics.html#has-one-association-reference。 您应该使用build_business，而不是由HAS_ONE

加在声明HAS_ONE协会business.build

4.2.1方法，声明类自动获取有关关联五个方法：

association(force_reload = false) 
association=(associate) 
build_association(attributes = {}) 
create_association(attributes = {}) 
create_association!(attributes = {}) 

Answer 2

一to One Association：

class User < ActiveRecord::Base 
    has_one :business 
end 

current_user.build_business 

或者如果一对多：

class User < ActiveRecord::Base 
    has_many :businesses 
end 

current_user.businesses.build