0

我是 ruby​​ on rails 的新手，我刚刚创建了一个小项目，用于添加、更新和删除 mysql db 中的记录

我能够成功地从 ruby​​ 应用程序的 mysql db 添加和删除记录

但问题只是当我尝试更新现有记录时

我的代码如下，

控制器：

class BookController < ApplicationController
def list
      @books = Book.find(:all)
   end
   def show
      @book = Book.find(params[:id])
   end
   def new
      @book = Book.new
      @subjects = Subject.find(:all)
   end
   def create
      @book = Book.new(params[:book])
      if @book.save
            redirect_to :action => 'list'
      else
            @subjects = Subject.find(:all)
            render :action => 'new'
      end
   end
   def edit
      @book = Book.find(:all)

      @subjects = Subject.find(:all)
   end
   def update
      @book = Book.find(params[:id])
      if @book.update_attributes(params[:book])
         redirect_to :action => 'show', :id => @book
      else
         @subjects = Subject.find(:all)
         render :action => 'edit'
      end
   end
   def delete
      Book.find(params[:id]).destroy
      redirect_to :action => 'list'
   end
   def show_subjects
      @subject = Subject.find(params[:id])
   end
end

列表 HTML：

<% if @books.blank? %>
<p>There are not any books currently in the system.</p>
<% else %>
<p>These are the current books in our system</p>
<ul id="books">
<% @books.each do |c| %>
<li>
<%= link_to c.title, {:action => 'show', :id => c.id} -%>

<b><%= link_to "edit",  {:action => 'edit', :id => c.id} %></b>

<b> <%= link_to "Delete", {:action => 'delete', :id => c.id},
:confirm => "Are you sure you want to delete this item?" %></b>
</li>
<% end %>
</ul>
<% end %>
<p><%= link_to "Add new Book", {:action => 'new' }%></p>


Edit HTML:
=========
<h1>Edit Book Detail</h1>
<%= form_tag(:action=> "update") do%>

<p><label for="book_title">Title</label>:
<%= text_field 'book', 'title' %></p>
<p><label for="book_price">Price</label>:
<%= text_field 'book', 'price' %></p>
<p><label for="book_subject">Subject</label>:
<%= collection_select(:book, :subject_id,
                         @subjects, :id, :name) %></p>
<p><label for="book_description">Description</label><br/>
<%= text_area 'book', 'description' %></p>
<%= submit_tag "Save changes" %>
<%end %>
<%= link_to 'Back', {:action => 'list' } %>

当我尝试从 URL 编辑记录时，出现以下异常http://localhost:3000/book/edit/5，

Showing C:/app/app/views/book/edit.html where line #5 raised:

undefined method `title' for #<Array:0x33315c0>
Extracted source (around line #5):

2: <%= form_tag(:action=> "update") do%>
3: 
4: <p><label for="book_title">Title</label>:
5: <%= text_field 'book', 'title' %></p>
6: <p><label for="book_price">Price</label>:
7: <%= text_field 'book', 'price' %></p>
8: <p><label for="book_subject">Subject</label>:

顺便说一句，我正在使用 rails3、ruby1.2 和 mysql5.5。

由于我处于学习曲线中，如果有人可以在这个问题上帮助我，那将非常有用。

4

1 回答 1

0

出于某种原因，当该edit方法的通常意图是编辑其中一个时，您正在加载所有书籍记录。

为了解决这个问题，你应该定义一个before_filter处理加载记录的钩子：

class BookController < ApplicationController
  # Set a handler for loading the book for most actions, except those
  # where loading a single book is not relevant.
  before_filter :load_book, :except => [ :index, :new, :create ]

  def edit
    @subjects = Subject.find(:all)
  end

  def update
    # Call the update_attributes method that will throw an exception if
    # an error occurs.
    @book.update_attributes!(params[:book])

    redirect_to :action => 'show', :id => @book

  rescue ActiveRecord::RecordInvalid
    # This exception is triggered if there was an error saving the record
    # because of a validation problem.

    # Trigger 'edit' action
    edit
    # Render as if on 'edit' page
    render :action => 'edit'
  end

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

需要注意的是，任何时候调用模型中的任何一个find(:all)或all在模型上调用时，都存在耗尽所有系统内存并使应用程序和运行它的服务器崩溃的风险。除非您可以确定记录的数量很少，否则分页是绝对必要的。

使用 abefore_filter可以更轻松地将各种冗余find调用合并到一个位置，并且可以使错误处理更简单。

于 2013-04-18T15:06:10.753 回答