控制器：

Question

我非常喜欢ruby on rails，我刚刚创建了一个小项目，它添加，更新和删除mysql db中的记录

我能够从ruby应用程序

成功添加和删除mysql数据库中的记录

但问题仅在于我尝试更新现有记录

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

列出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' } %>

当我尝试编辑来自网址http://localhost:3000/book/edit/5的记录

时，我收到以下异常

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>:

BTW我使用的是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。

Answer 1

出于某种原因，当edit方法的通常用途是编辑其中一个时，您正在加载所有图书记录。

要解决此问题，您应该定义一个处理加载记录的before_filter挂钩：

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

请注意，只要您在模型上调用find(:all)或all，就会冒着耗尽所有系统内存并使应用程序及其运行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before_filter可以更轻松地将各种冗余find调用合并到一个位置，并且可以简化错误处理。

无法在轨道上的ruby中执行编辑操作

控制器：

列出HTML：

1 个答案: