Question

我在使用Rails项目时遇到了一些麻烦。我正在尝试为新主题进行验证。它应该至少有四个字符的主题，但我收到一个错误的用户。这是我的错误：

2.2.0 :019 > t=Topic.new
 => #<Topic id: nil, name: nil, public: nil, description: nil, created_at: nil, updated_at: nil> 
2.2.0 :020 > t.valid?
NoMethodError: undefined method `user' for #<Topic:0x007ff53fb9e268>
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activemodel-4.2.0/lib/active_model/attribute_methods.rb:433:in `method_missing'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activemodel-4.2.0/lib/active_model/validator.rb:149:in `block in validate'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activemodel-4.2.0/lib/active_model/validator.rb:148:in `each'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activemodel-4.2.0/lib/active_model/validator.rb:148:in `validate'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activerecord-4.2.0/lib/active_record/validations/presence.rb:5:in `validate'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:450:in `public_send'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:450:in `block in make_lambda'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:189:in `call'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:189:in `block in simple'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:190:in `call'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:190:in `block in simple'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:190:in `call'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:190:in `block in simple'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:190:in `call'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:190:in `block in simple'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/callbacks.rb:92:in `call'
... 21 levels...
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:268:in `load'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:268:in `block in load'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:268:in `load'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/commands/rails.rb:6:in `call'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/command_wrapper.rb:38:in `call'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/application.rb:183:in `block in serve'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/application.rb:156:in `fork'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/application.rb:156:in `serve'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/application.rb:131:in `block in run'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/application.rb:125:in `loop'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/application.rb:125:in `run'
    from /Users/ericpark/.rvm/gems/ruby-2.2.0/gems/spring-1.3.4/lib/spring/application/boot.rb:18:in `<top (required)>'
    from /Users/ericpark/.rvm/rubies/ruby-2.2.0/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /Users/ericpark/.rvm/rubies/ruby-2.2.0/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'

我的主题控制器：

class TopicsController < ApplicationController
  def index
    @topics = Topic.all
    authorize @topics
  end

  def new
    @topic = Topic.new
    authorize @topic
  end

  def show
    @topic = Topic.find(params[:id])
      @posts = @topic.posts
    authorize @topic
  end

  def edit
    @topic = Topic.find(params[:id])
     authorize @topic
  end

  def create
    @topic = Topic.new(topic_params)
     authorize @topic
     if @topic.save
       redirect_to @topic, notice: "Topic was saved successfully."
     else
       flash[:error] = "Error creating topic. Please try again."
       render :new
     end
  end

  def update
    @topic = Topic.find(params[:id])
     authorize @topic
     if @topic.update_attributes(topic_params)
       redirect_to @topic
     else
       flash[:error] = "Error saving topic. Please try again."
       render :edit
     end
  end

  private
  def topic_params
    params.require(:topic).permit(:name, :description, :public)
  end
end

主题模型：

class Topic < ActiveRecord::Base
  has_many :posts
  belongs_to :user

  validates :name, length: {minimum: 5}, presence: true
end

我不确定为什么它声明NoMethodError：未定义的方法'user'，我认为主题不需要用户方法，因为它不是主题的属性之一。任何帮助和解释将不胜感激！提前谢谢！

Answer 1

您可能缺少用户模型。

应用程序/模型/ user.rb

class User < ActiveRecord::Base
  has_many :topics
  has_many :posts
end

用户对新字符串没有方法错误

1 个答案: