為什么不是這部分HTML渲染，為什么我得到一個未定義的方法`cardsets'為nil：Rails中的NilClass？

Question

我正在嘗試在Rails中添加一個flashcards（cardsets）功能，我在實現這個時遇到了一些問題，因為我得到一個undefined method cardsets'為nil：NilClass`錯誤

如果我改變，我可以讓頁面呈現： <% if @user.cardsets.any? %> <% if @user.cardsets.any? %>到<% unless @cardsets.any? %> <% unless @cardsets.any? %>但是當我這樣做時會顯示相應的卡片組。 以下是產生此錯誤的html.erb代碼：

<% provide(:title, "Flashcards") %>
<h1>Flashcards</h1>

<div class="row">
  <aside class="span3">
    <%= render "shared/cardset_form" %>
  </aside>
  <div class="span6">
    **<% if @user.cardsets.any? %>**
        <h3>Flashcard Sets (<%= @user.cardsets.count %>)</h3>
        <ol class="cardsets">
          <% @user.cardsets.each do |cardset| %>
              <li>
                <span class="topic"><%= link_to cardset.topic, show_cardset_path(cardset) %></span>
                <%= link_to "edit", edit_cardset_path(cardset) %>
                <%= render partial: "shared/delete_link", locals: {item: cardset} %>
              </li>
          <% end %>
        </ol>
    <% end %>
  </div>
</div>

我已經為nil：NilClass`錯誤生成了undefined method cardsets的行。

這就是我的cardsets_controller.rb中的內容：

class CardsetsController < ApplicationController
  before_action :signed_in_user, only: [:new, :index, :create, :edit, :destroy, :update]
  before_action :correct_user, only: [:edit, :update, :destroy]

  def index
    @cardsets = Cardset.all
  end

  def show
    @cardset = Cardset.find(params[:id])
  end

  def create
    @cardset = current_user.cardsets.build(cardset_params)
    if @cardset.save
      flash[:success] = "A new set of flashcards have been created!"
      redirect_to @cardset
    else
      render "new"
    end
  end

  def new
    @cardset = Cardset.new
  end

  def edit
  end

  def update
    @cardset = Cardset.find(params[:id])
    if @cardset.update_attributes(cardset_params)
      flash[:success] = "You've updated your flashcards!"
      redirect_to @cardset
    else
      render "edit"
    end
  end

  def destroy
    @cardset = Cardset.find(params[:id])
    @cardset.delete
    redirect_to cardsets_path
  end

  private

    def cardset_params
      params.require(:cardset).permit(:topic, :description)
    end

    def correct_user
      @cardset = current_user.cardsets.find_by_id(params[:id])
      redirect_to root_url if @cardset.nil?
    end
end

這是我的cardset.rb文件中的代碼：

class Cardset < ActiveRecord::Base
  belongs_to :user
  validates :user_id, presence: true
  validates :topic, presence: true
end

這是我的user.rb文件中的代碼：

class User < ActiveRecord::Base
  has_many :cardsets
  (...a bunch of other code...) 
end

如果有人能就我可能出錯的地方提供一些幫助或建議，我將非常感激！

謝謝！

Answer 1

據我所知，你沒有在你的Controller中設置@user ，所以@user是nil 。

您可能想要定義@user或者您打算使用@cardsets 。