Unable to perform edit operation in ruby on rails - mysql

Question

I am very new bee to ruby on rails, i have just created a small project which add,update and delete a record from mysql db
I am able to successfully add and delete record from mysql db from ruby application
But the issue is only when i try to update the existing record
My code is as follows,
Controller:
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
List 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' } %>
I am getting the following exception when i try to edit a record from URL 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>:
BTW i am using rails3,ruby1.2 and mysql5.5.
As i am in a learning curve, it will be very useful if some one can help me in this issue.

Answer 1

For some reason you're loading all the book records when the usual intention of the edit method is to edit one of them.
To fix this, you should define a before_filter hook that handles loading records:
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
As a note, any time you call either find(:all) or all on a model, you run the risk of using up all the system memory and crashing both your application and the server it's running on. Pagination is absolutely essential unless you can be certain the number of records is small.
Using a before_filter makes it a lot easier to consolidate your various redundant find calls into one place and can make error handling a lot simpler.