Question

我想添加＆＃34;类别＆＃34;功能。我关联了article.rb和category.rb。但是，未定义的方法`类别＆＃39;为零：NilClass在场。我不知道。如果您知道任何解决方案，请告诉我。

Index.html.erb

   <% unless @article.categories.blank? %>
         <% @articles.categories.each do |category|%>
             <%= link_to category.name,article_path(category_id:category.id)%>
         <%end%>
       <%end%>

article.rb

class Article < ApplicationRecord
  scope :from_category, -> (category_id)  { where(id: article_ids = ArticleCategory.where(category_id: category_id).select(:article_id))}
  validates :title, presence: true
  validates :content, presence: true
  mount_uploader :image,ImageUploader
  has_many :categories, through: :article_categories
  has_many :article_categories, dependent: :destroy

  def save_categories(tags)
    current_tags = self.categoires.pluck(:name) unless self.categories.nil?
    old_tags = current_tags - tags
    new_tags = tags - current_tags

    old_tags.each do |old_name|
      self.categories.delete Category.find_by(name:old_name)
    end

    new_tags.each do |new_name|
      article_category = Category.find_or_create_by(name:new_name)
      self.categories << article_category
    end

  end

end

category.rb

class Category < ApplicationRecord
  validates :name,presense: true,length:{maximum:50}
  has_many :articles,through: :article_categories
  has_many :article_categories,dependent: :destroy
end

article_category.rb

class ArticleCategory < ApplicationRecord
  belongs_to :article
  belongs_to :category
  validates :article_id,presense:true
  validates :category_id,presense:true
end

articles_controller.rb

class ArticlesController < ApplicationController

  before_action :set_post, only: [:show,:edit,:update]
  before_action :authenticate_user!, :except => [:index,:show]
  before_action :set_article_tags_to_gon, only: [:edit]

  def index
    if params[:category_id]
      @selected_category = Category.find(params[:category_id])
      @articles= Article.from_category(params[:category_id]).page(params[:page])
    else
      @articles= Article.all.page(params[:page])
    end
    @articles = Article.page params[:page]
  end

  def show
  end

  def new
    @article = Article.new
  end

  def create
    @article = Article.new(article_params)
    if @article.save
    redirect_to articles_path
    else
      render 'articles/new'
    end
  end

  def edit
    @category_list = @article.categories.pluck(:name).join(",")
  end

  def update
    if @article.update(article_params)
      redirect_to articles_path
    else
      redirect_to 'edit'
    end
  end

  private
  def article_params
    params[:article].permit(:title,:content,:image,:tag_list,:category)
  end

  def set_post
    @article = Article.find(params[:id])
  end

error message

Answer 1

您在nil对象上调用类别，在本例中为@article。你的意思是在@articles上打电话吗？

如果没有，则需要在控制器的@article操作中定义index。

Rails Association未定义的方法错误

1 个答案: