Question

我在rails中的Book表单中收到此错误：

表单中的第一个参数不能包含nil或为空

表格的

<%= form_for @book, html: { multipart: true } do |f| %>
  <% if @book.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@book.errors.count, "error") %> prohibited this book from being saved:</h2>

      <ul>
      <% @book.errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </div>
  <div class="field">
    <%= f.label :author %><br>
    <%= f.text_field :author %>
  </div>
  <div class="field">
    <%= f.label :language %><br>
    <%= f.text_field :language %>
  </div>
  <div class="field">
    <%= f.label :year %><br>
    <%= f.text_field :year %>
  </div>
  <div class="field">
    <%= f.label :description %><br>
    <%= f.text_area :description %>
  </div>
  <div class="field">
    <%= f.label :total_pages %><br>
    <%= f.text_field :total_pages %>
  </div>
  <div class="field">
    <%= f.label :rating %><br>
    <%= f.text_field :rating %>
  </div>
  <div class="field">
    <%= f.label :image %><br>
    <%= f.file_field :image %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>

<% end %>

控制器

class BooksController < ApplicationController
  before_action :set_book, only: [:show, :edit, :update, :destroy]
  before_action :authenticate_user!, except: [:index, :show]



  def search
    if params[:search].present?
      @books = Book.search(params[:search])
    else
      @books = Book.all
    end
  end


  def index
    @books = Book.all
  end


  def show
    @reviews = Review.where(book_id: @book.id).order("created_at DESC")

      if @reviews.blank?
        @avg_review = 0
      else
        @avg_review = @reviews.average(:rating).round(2)
    end
  end

  end


  def new
    @book = current_user.books.build
  end


  def edit
  end


  def create
    @book = current_user.books.build(book_params)

    respond_to do |format|
      if @book.save
        format.html { redirect_to @book, notice: 'Book was successfully created.' }
        format.json { render :show, status: :created, location: @book }
      else
        format.html { render :new }
        format.json { render json: @book.errors, status: :unprocessable_entity }
      end
    end
  end


  def update
    respond_to do |format|
      if @book.update(book_params)
        format.html { redirect_to @book, notice: 'Book was successfully updated.' }
        format.json { render :show, status: :ok, location: @book }
      else
        format.html { render :edit }
        format.json { render json: @book.errors, status: :unprocessable_entity }
      end
    end
  end


  def destroy
    @book.destroy
    respond_to do |format|
      format.html { redirect_to books_url, notice: 'Book was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

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

    def book_params
      params.require(:book).permit(:title, :author, :language, :year, :description, :total_pages, :rating, :image)
    end

我遇到了相关错误，但没有一个解决方案似乎符合我的特定问题。可能导致这种情况的任何线索？

Answer 1

您收到错误是因为@book为零。

确保您已使用相应控制器@book中的@book = Book.new初始化action，以便@book可用于包含该表单的视图。

Answer 2

在控制器操作中初始化@book = Book.new

表单中的第一个参数不能包含nil或为空

2 个答案: