在軌道中使用回形針寶石時出現NoMethodError

Question

我正嘗試使用回形針中的回形針gem和imagemagick上傳圖像。我做了所有我應該做的事情，當我嘗試上傳時，出現以下錯誤消息。這是一個NoMethodError。 Error message screenshot

我的寶石文件：

source 'https://rubygems.org' 
gem 'rails', '4.2.3' 
gem 'sqlite3' 
gem 'simple_form', '~> 3.4' 
gem 'sass-rails', '~> 5.0' 
gem 'uglifier', '>= 1.3.0' 
gem 'coffee-rails', '~> 4.1.0' 
gem 'jquery-rails' 
gem 'turbolinks' 
gem 'devise', '~> 4.2', '>= 4.2.1' 
gem 'bootstrap-sass', '~> 3.3.4.1' 
gem 'coffee-script-source', '1.8.0' 
gem 'jbuilder', '~> 2.0' 
gem 'paperclip', '~> 5.1' 
gem 'sdoc', '~> 0.4.0', group: :doc 
gem 'bcrypt', git: 'https://github.com/codahale/bcrypt-ruby.git', :require => 'bcrypt' 

group :development, :test do 
    gem 'byebug' 
    gem 'web-console', '~> 2.0' 
end 

gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby] 

我_form.html.erb文件：

<%= simple_form_for @book, :html => { :multipart => true } do |f| %> 
    <%= select_tag(:category_idd, options_for_select(@categories), :prompt=> "Select a category")%> 
    <%= f.file_field :book_img%> 
    <%= f.input :title, label: "Book title" %> 
    <%= f.input :description, label: "Please describe your book here"%> 
    <%= f.input :author, label: "Who is the author of this book?" %> 
    <%= f.button :submit%> 
<% end %> 

我development.rb文件：

Rails.application.configure do 

    Paperclip.options[:command_path] = 'C:\Program Files (x86)\GnuWin32\bin' 

    config.cache_classes = false 

    config.eager_load = false 


    config.consider_all_requests_local  = true 
    config.action_controller.perform_caching = false 

    config.action_mailer.raise_delivery_errors = false 

    config.active_support.deprecation = :log 

    config.active_record.migration_error = :page_load 

    config.assets.debug = true 

    config.assets.digest = true 


    config.assets.raise_runtime_errors = true 

end 

我book.rb文件：

class Book < ActiveRecord::Base 
    belongs_to :user 
    belongs_to :category 

    has_attached_file :book_img, styles: { medium: "300x300>", thumb: "100x100>" }, default_url: "/images/:style/missing.png" 
    validates_attachment_content_type :book_img, content_type: /\Aimage\/.*\z/ 
end 

我book_controller文件：

class BooksController < ApplicationController 
    before_action :find_book, only: [:show, :edit, :update, :destroy] 

    def index 
     if params[:category].blank? 
      @books = Book.all.order("created_at DESC") 
     else 
      @category_idd = Category.find_by(name: params[:category]).id 
      @books = Book.where(:category_idd => @category_idd).order("created_at DESC") 
     end 
    end 
    def show 
    end 

    def new 
     @book = current_user.books.build 
     @categories = Category.all.map{ |c| [c.name, c.id]} 
    end 

    def create 
     @book = current_user.books.build(book_params) 
     @book.category_idd = params[:category_idd] 

     if @book.save 
      redirect_to root_path 
     else 
      render 'new' 
     end 
    end 

    def edit 
     @categories = Category.all.map{ |c| [c.name, c.id]} 
    end 

    def update 
     @book.category_idd = params[:category_idd] 
     if @book.update(book_params) 
      redirect_to book_path(@book) 
     else 
      render 'edit' 
     end 
    end 

    def destroy 
     @book.destroy 
     redirect_to root_path 
    end 

    private 

     def book_params 
      params.require(:book).permit(:title, :description, :author, :category_idd, :book_img) 
     end 

     def find_book 
      @book = Book.find(params[:id]) 
     end 
end 

要注意，當我刪除的東西「：book_image」從book_controller的book_params，錯誤消失，但我不認爲它實際上自從上傳圖像本書的參數必須包含「：book_img」部分。幫助將不勝感激，因爲這讓我瘋狂。

編輯： 從books_controller中的book_params中刪除：book_img後，我嘗試提交附帶圖像的表單。我沒有遇到任何錯誤，但是當我轉到rails控制檯並查看上一本上傳圖書中的數據時，它們顯示與「book_img」相關的數據全部爲「無」。所以即使錯誤消失了，圖像也沒有上傳。

EDIT2：冰人，我得到以下錯誤：Error image screenshot

Answer 1

這部分是問題，當@book不會被保存形式進行重新渲染和@categories是nil。添加一個電話獲取@categories，你應該很好去。

if @book.save 
    redirect_to root_path 
else 
    @categories = Category.pluck(:name, :id) 
    render 'new' 
end