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我在我的項目上收到以下錯誤：表單中的第一個參數不能包含零或爲空。我正在嘗試爲我的代碼創建一個編輯頁面。 Rails相當新穎，並嘗試在沒有腳手架的情況下學習。Rails 4：收到以下錯誤：表單中的第一個參數不能包含零或爲空
控制器：
class BooksController < ApplicationController
def new
@book = Book.new
@authors = Author.all
end
def edit
@book = Book.find(params[:id])
end
def show
#Notice how the @books is plural here.
@books = Book.all
@authors = Author.all
#@books = Book.where(id: params[:id])
end
#Create method will save new entries
def create
@book = Book.new(book_params)
@authors = Author.all
if @book.save
flash[:success] = "Book Added to Databse!"
redirect_to @book
else
render 'new'
end
end
private
#Note that this method will go up into the create method above.
def book_params
params.require(:book).permit(:title, :pub_date, :publisher, :author_id)
end
end
模型Page：（對於書）
class Book < ActiveRecord::Base
validates :title, :pub_date, :publisher, presence: true
validates :title, uniqueness: true
belongs_to :author
end
模型Page：（對於作者）
class Author < ActiveRecord::Base
validates :name, presence: true
validates :name, uniqueness: true
has_many :books
end
編輯頁：
<h1>Update a book entry</h2>
<div class="row">
<div class="col-md-6 col-md-offset-3">
<%= form_for(@book) do |f| %> **ERROR SEEMS TO BE RIGHT HERE!!!**
<%= render 'form' %>
<div class="form-group">
<%= f.label :title %>
<%= f.text_field :title, class: 'form-control' %>
</div>
<div class="form-group">
<%= f.label :pub_date %>
<%= f.text_field :pub_date, class: 'form-control' %>
</div>
<div class="form-group">
<%= f.label :publisher %>
<%= f.text_field :publisher, class: 'form-control' %><br />
</div>
<div class="form-group">
<%= f.select(:author_id,
@authors.collect {|a| [ a.name, a.id ]},
{:include_blank => 'Please select an author'},
class: "form-control") %><br />
</div>
<%= f.submit 'Save Changes', class: "btn btn-primary" %>
<% end %>
</div>
</div>
渲染表單頁面（_form.html.erb）
<% if @book.errors.any? %>
<div id="error_explanation">
<div class="alert alert-danger">
<h2><%= pluralize(@book.errors.count, "error") %>
prohibited this entry from being saved:</h2>
<ul>
<% @book.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
</div>
<% end %>
顯示頁面：
<div class="move">
<h1>Showing Book Titles:</h1>
</div><br />
<div class="row">
<% @books.each do |book| %>
<div class="col-md-4">
<div class="panel panel-default">
<div class="panel-body">
<h2><%= book.title %></h2>
<h2><%= book.publisher %></h2>
<h2><%= book.pub_date %></h2>
<h2><%= book.author.name %></h2>
<h2><%= link_to "Edit", edit_path, class: "btn btn-primary" %>
</div>
</div>
</div>
<% end %>
這裏是我的日誌，告訴我什麼是錯的：
Started GET "/edit" for ::1 at 2015-08-14 16:49:17 -0400
Processing by BooksController#edit as HTML
Rendered books/edit.html.erb within layouts/application (2.2ms)
Completed 500 Internal Server Error in 9ms (ActiveRecord: 0.0ms)
ActionView::Template::Error (First argument in form cannot contain nil or be empty):
3: <div class="row">
4: <div class="col-md-6 col-md-offset-3">
5:
6: <%= form_for(@book) do |f| %>
7: <%= render 'form' %>
8:
9: <div class="form-group">
app/views/books/edit.html.erb:6:in `_app_views_books_edit_html_erb___525891009649529081_70260522100960'
我會說我已經從我的數據庫中刪除了前14本書，所以第一本書從ID 14開始。不知道這是否重要。
最後，我試圖在編輯方法將所有這些不同的實例變量的給我的控制器：
#@book = Book.where(id: params[:id])
#@book = Book.find_by_id(params[:id])
#@book = Book.all
#@book = Book.find_by_id(params[:id])
#book = Book.new(book_params)
#When I use the two below lines,
there are no error pages but create a new entry.
#@book = Book.new
#@authors = Author.all
任何幫助將不勝感激！感謝您的時間！！！
您正在編輯的書可能不在您的數據庫中。您的網址中的圖書ID是什麼？你確定這本書存在於你的數據庫中嗎？您可以通過Rails控制檯進行確認。 –
在添加編輯功能之前，我確實在我的數據庫中有書。一旦我添加了編輯功能，我刪除了書籍，然後添加了一個。 （這是一本ID爲14的書，它是數據庫中唯一的一本書，我可以在我的顯示頁面上點擊它的編輯按鈕，那就是當我得到死亡的紅色頁面時 –
即使我添加了一本新書，我剛剛做了，我得到以下錯誤信息：當我點擊它的編輯按鈕時，無法找到帶有'id'= id的書。令人沮喪但是學習的痛苦的一部分 –