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Implementing Tagging Support

In this third part to a four-part article series on implementing tagging support for an ecommerce website using Ruby-on-Rails, you'll learn how to set up the application so users can assign tags to items. This article is excerpted from chapter seven of the book Practical Rails Projects, written by Eldon Alameda (Apress; ISBN: 1590597818).

Author Info:
By: Apress Publishing
Rating: 5 stars5 stars5 stars5 stars5 stars / 2
June 10, 2010
  1. · Implementing Tagging Support
  2. · Modifying the View
  3. · Modifying the Controller
  4. · Changing the Style Sheet

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Implementing Tagging Support - Modifying the Controller
(Page 3 of 4 )

You can now try to access the page with your browser. It should generate the following error, as the view expects to find the tags instance variable:

You have a nil object when you didn't expect it!

Fix this by changing theloadmethod in the book controller (app/controllers/admin/ book_controller.rb), as follows:

  def load_data
    @authors = Author.find(:all)
    @publishers = Publisher.find(:all)

    @tags = Tag.find(:all)

Recall that we use theload_datamethod to load all authors, publishers, and tags in thenewandeditactions. Now, if you openhttp://localhost:3000/admin/book/new, you should see the new field.

Add a book and type in a few tags, such asProgramming, Rails, Ruby. Save the book, and create another book. Type the character R  in the Tags field. This time, you should see a list of tags containing both Rails and Ruby.

Note  As stated earlier, this example does not use Ajax. Instead, the tags are all stored in a JavaScript variable. Using Ajax would be easier. The autocompletion text field could be generated with the following code:<%= text_field_with_auto_complete :book, :tags %>This would also require us to add theauto_complete_for_book_tagsaction to the controller, which would render a partial view.

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