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CRUD With Scaffolding


    At the core, most database driven web sites are the same. They need to store records and provide a way to do the following:

    • Create new records in the database
    • Read or show the records in the database
    • Update existing records
    • Destroy or delete records

    Because these 4 actions (CRUD) are so common, rails includes the scaffold command to make creating them easier.


Step 1

Type this in the terminal:
rails server

Step 2

Point your browser to http://localhost:3000/topics

You should see a page listing topics that looks something like this:

Step 3

  • Click on "New Topic"
  • Fill in the form and click "Create Topic"
  • You should see a confirmation page like this:

Step 4

  • Click on "back"
  • You should see the topic list again, this time with your new topic listed:

  • Try the 'show', 'edit', and 'destroy' links to see what they do
  • You've created a basic database driven web site, congrats!


How did all those pages get created and hooked together? The rails scaffold did it for you.

Let's take a closer look at some of the files rails created:

  • app/models/topic.rb

    • This file contains code for our topic model. If you look at it, it's nearly blank. Creating, reading, updating, and deleting records are built into rails.
  • app/views/topics

    • This folder contains all the views for our topics model. This is where the code for the forms you used above is stored. Rails created all of these pages as part of the scaffold.
    • If you've written HTML before, many lines in the views should look familiar. Rails views are HTML with some extra code added to display data from the database.
  • app/views/topics/index.html.erb

    • This is the code for the page that lists all the topics.
    • Index is the name given to the "default" page for a web site or a section of a web site. When you navigate to http://localhost:3000/topics the topics index page is what is sent to your computer.
  • app/views/topics/show.html.erb

    • This is the page you get when you click the "show" link on the "Listing topics" page.
  • app/views/topics/new.html.erb

    • This is the page you get when you click on "New Topic".
  • app/views/topics/edit.html.erb

    • This is the page you get when you click on "Edit"
  • app/views/topics/_form.html.erb

    • You may have noticed that the page for new topics and the page to edit topics looked similar. That's because they both use the code from this file to show a form. This file is called a partial since it only contains code for part of a page. Partials always have filenames starting with an underscore character.
  • Challenge question: Can you find the line of code in new.html.erb and edit.html.erb that makes the form partial appear?

  • app/controllers/topics_controller.rb

    • This is the controller file that rails created as part of the scaffold
    • If you look you'll see a method (a line beginning with def) for each of the views listed above (except _form.html.erb)

Next Step:

Back to Creating A Migration

If you find something that could be improved, please make a pull request or drop us a note via GitHub Issues (no technical knowledge required).

Source: https://github.com/RailsBridge-CapeTown