Rolling with Ruby on Rails

MySQL-Front is a graphical interface for the MySQL database. It is an inexpensive commercial application, but you can try it for free for 30 days. In this article, we will use MySQL-Front to develop our database. If you prefer, you can also just send SQL commands to the database from the command line.

1. Download the latest version of MySQL-Front (currently, version 3.1).
2. Double-click on the downloaded executable and follow the installation instructions (Figure 5). Unless you have some special needs, you can accept all of the defaults.

Figure 5. MySQL-Front installer

Essential Reading Building Tag Clouds in Perl and PHP By Jim Bumgardner Tag clouds are everywhere on the web these days. First popularized by the web sites Flickr, Technorati, and del.icio.us, these amorphous clumps of words now appear on a slew of web sites as visual evidence of their membership in the elite corps of "Web 2.0." This PDF analyzes what is and isn't a tag cloud, offers design tips for using them effectively, and then goes on to show how to collect tags and display them in the tag cloud format. Scripts are provided in Perl and PHP. Yes, some have said tag clouds are a fad. But as you will see, tag clouds, when used properly, have real merits. More importantly, the skills you learn in making your own tag clouds enable you to make other interesting kinds of interfaces that will outlast the mercurial fads of this year or the next. Read Online--Safari Search this book on Safari:   Only This Book All of Safari Code Fragments only

Let's Write Code

We'll create an online collaborative cookbook for holding and sharing everyone's favorite recipes. We want our cookbook to:

• Display a list of all recipes.
• Create new recipes and edit existing recipes.
• Assign a recipe to a category (like "dessert" or "soup").

You can create your cookbook application in any directory you like, but I used c:\rails\cookbook. All paths used in this article assume this base directory path. If you choose a different location, be sure to make the necessary adjustments as you see application paths in this article.

If you like, you can download the complete Rails cookbook example and follow along. If you do this, look in the cookbook/db/ directory for a file to use to rebuild the database.

Creating an Empty Rails Web Application

Rails is both a runtime web app framework and a set of helper scripts that automate many of the things you do when developing a web application. In this step, we will use one such helper script to create the entire directory structure and the initial set of files to start our cookbook application.

1. Open a command window and navigate to where you want to create this cookbook web application. I used c:\rails.

2. Run the command:

   rails cookbook

   This will create a cookbook subdirectory containing a complete directory tree of folders and files for an empty Rails application.

Figure 6. A newly created Rails application directory

Testing the Empty Web Application

A Rails web application can run under virtually any web server, but the most convenient way to develop a Rails web application is to use the built-in WEBrick web server. Let's start this web server and then browse to our cookbook application.

• In your open command window, move into the cookbook directory.

• Run the command:

  ruby script\server

  to start the server (Figure 7).

• Now open your browser and browse to http://127.0.0.1:3000/. You should see something like Figure 8. [Editor's note: Unless you're following along with the article, these links probably won't work for you. Don't panic--127.0.0.1 is a special address reserved for the local machine.]

Figure 7. Starting the WEBrick server

Leave the command window open and the web server running, as we will be using it as we proceed.

Figure 8. The Rails default page

A Rails Application's Directory Structure

Rails tries very hard to minimize the number of decisions you have to make and to eliminate unnecessary work. When you used the rails helper script to create your empty application, it created the entire directory structure for the application (Figure 9). Rails knows where to find things it needs within this structure, so you don't have to tell it. Remember, no configuration files!

Figure 9. A Rails application directory structure

Most of our development work will be creating and editing files in the c:\rails\cookbook\app subdirectories. Here's a quick rundown of how to use them.

• The controllers subdirectory is where Rails looks to find controller classes. A controller handles a web request from the user.
• The views subdirectory holds the display templates to fill in with data from our application, convert to HTML, and return to the user's browser.
• The models subdirectory holds the classes that model and wrap the data stored in our application's database. In most frameworks, this part of the application can grow pretty messy, tedious, verbose, and error-prone. Rails makes it dead simple!
• The helpers subdirectory holds any helper classes used to assist the model, view, and controller classes. This helps to keep the the model, view, and controller code small, focused, and uncluttered.

Controllers and URLs

In a moment, we will create our cookbook database and begin developing our application. First, it's important to understand how controllers work in Rails and how URLs map into (and execute) controller methods.

Controller classes handle web requests from the user. The URL of the request maps to a controller class and a method within the class. How does this work?

Leave your existing command window open with the web server running, open a second command window, and navigate to the application's base directory, c:\rails\cookbook. It will look like Figure 10, at least in a moment.

Figure 10. The cookbook controller directory

We will use another Rails helper script to create a new controller class for us. In the command window, run the command:

ruby script\generate controller MyTest

This will create a file named my_test_controller.rb containing a skeleton definition for the class MyTestController.

In the c:\rails\cookbook\controllers directory, right-click on this file and choose Edit. The file should resemble Figure 11.

Figure 11. Editing MytestController

What happens if you browse to something that you know does not exist? Try http://127.0.0.1:3000/garbage/. Figure 12 shows the results.

Figure 12. Browsing to an unknown controller

That's not too surprising. Now try http://127.0.0.1:3000/My_Test/, shown in Figure 13.

Figure 13. Browsing to the new controller

Hmmm. Now that's different. The Mytest part of the URL maps to the newly created controller. Now it seems that Rails tried to find an action named index in this controller but couldn't.

Let's fix that. Add an index method to your controller class as in Figure 14.

Figure 14. The index method of MytestController

Refresh your browser, and you should now see something more like Figure 15.

Figure 15. The result of the index method

You will have the same results with http://127.0.0.1:3000/My_Test/index, too.

Let's add another action to the controller just to make sure you have the idea. Add the dilbert method from Figure 16.

Figure 16. The dilbert method

Now browse to http://127.0.0.1:3000/My_Test/dilbert and you'll see something like Figure 17.

Figure 17. The output of the dilbert method

I think you have the idea.

Let's create our database now and work on some real pieces of our cookbook application.

Creating the Cookbook Database

It's time to create the cookbook database and tell Rails how to find it. (This is the only configuration that you will find in Rails.)

1. Start MySQL-Front and log in to your locally running MySQL instance (localhost) as root, using an empty password. You should see something like Figure 18.

   
   Figure 18. MySQL-Front

2. There are two existing databases, mysql and test. Create a new database named cookbook. Execute the menu command Database>New>Database... and enter the database name cookbook, as Figure 19 illustrates.

   
   Figure 19. Creating a new database

   Click Ok to create the database.

3. To tell Rails how to find the database, edit the file c:\rails\cookbook\config\database.yml and change the database name to cookbook. Leave the username as root and the password empty. When you finish, it should look something like Figure 20.

   
   Figure 20. The database.yml configuration file

Rails lets you run in development mode, test mode, or production mode, using different databases. This application uses the same database for each.

Editor's note: A recent change in Rails requires that you restart the webserver, or else Rails will never see the new database and the subsequent steps will fail. Hit Ctrl-C or close the window as appropriate and relaunch the web server at this point.

Creating the recipes Table

Our cookbook will contain recipes, so let's create a table in our database to hold them.

In the left-hand pane of MySQL-Front, right click on the cookbook database you just created and select New>Table... from the pop-up menu (Figure 21).

Figure 21. Creating a new table

Name the table recipes (Figure 22).

Figure 22. The Add Table dialog box

Important note: MySQL-Front will automatically create a primary key named Id, but Rails prefers to call it id (all lowercase). I'll explain more later, but for now just change it. In the left pane, select the recipes table you just created. In the right pane, right-click on the Id field, select Properties (Figure 23), and change the name to id.

Figure 23. Renaming the primary key

Adding Recipe Fields

Now that we have a recipes table, we can start adding fields (columns) to hold recipe data. Let's start by creating title and instructions fields. Eventually, we will need more fields, but this is a good place to start.

With the recipe table selected, right click in a blank area of the right pane and select New>Field... (Figure 24).

Figure 24. Adding a new field

Create the recipe title field as a varchar(255) with nulls not allowed, so that every recipe must have title text. Figure 25 shows the options in the pop-up window.

Figure 25. Adding the title field

Repeat the above procedure to create an instructions field as text, as shown in Figure 26.

Figure 26. Adding the instructions field

The recipe table should now resemble Figure 27.

Figure 27. The modified recipe table

The Excitement Begins

Everything we have done up to this point has been pretty short and painless, but not particularly exciting. This is where that changes. We can now have the very beginnings of our cookbook application up and running in record time!

Create the Model

First, create a Recipe model class that will hold data from the recipes table in the database. Figure 28 shows where it should live.

Figure 28. The Recipe model class

Open a command window to the cookbook directory (c:\rails\cookbook) and run the command:

ruby script\generate model Recipe

This will create a file named recipe.rb containing a skeleton definition for the Recipe class. Right-click on this file and choose Edit to look inside (Figure 29).

Figure 29. The contents of recipe.rb

This seemingly empty class definition is the recipe business object that Rails maps to the recipes table in the database. You will see more concretely what I mean by this in a moment. Right now, I want to point out that this little bit of programming magic happened because we used a Rails naming convention: a singular model class name (Recipe) maps to a plural database table (recipes). Rails is smart about English pluralization rules, so Company maps to companies, Person maps to people, and so forth.

Further, Rails dynamically populates the Recipe class with methods for accessing the rows in the recipes table and an attribute for each column in the table.

Very shortly, you will see a dramatic demonstration of this dynamic connection between the Recipe class and the recipes table.

We are now very close to seeing something work. We need to create a recipe controller (Figure 30) with actions to manipulate the recipes in the database via the standard CRUD operations: create, read, update, and delete. Rails makes this easier than you might think.

Figure 30. The Recipe controller in its native environment

Open a command window in the cookbook directory (c:\rails\cookbook) and run the command:

ruby script\generate controller Recipe

This will create a file named recipe_controller.rb containing a skeleton definition for the RecipeController class. Right-click on this file, choose Edit, and add the line scaffold :recipe as shown in Figure 31.

Figure 31. One line of code in RecipeController

This single line of code will bring the database table to life. It defines actions for all CRUD operations, immediately allowing us to create, read, update, and delete recipes in our database!

Open a browser and navigate to http://127.0.0.1:3000/recipe/new. You should see something like Figure 32.

Figure 30. Creating a new recipe page

Now this is pretty cool! We haven't done much of anything and we can already start to populate our database. Don't do that just yet, though. Let's add a few more fields to the recipe table first.

Use MySQL-Front to add description and date fields between the title and instructions fields (Figures 33 and 34).

Figure 33. Adding the description field

Figure 34. Adding the date field

Refresh your browser to see a page similar to Figure 35.

Figure 35. A new recipe page with the new fields

Now, that is way beyond cool--it's awesome!

OK, calm down and enter a test recipe. Fill in the fields as shown in Figure 36 and click on the Create button.

Figure 36. A new recipe

You should see the results, as in Figure 37.

Figure 37. A listing of all recipes

Add another one by clicking the "New recipe" link and entering the data, as in Figure 38.

Figure 38. Another new recipe

After you click Create you should see something like Figure 39.

Figure 39. A fuller list of all recipes

We now have an amazing amount of functionality, by merely building a database table and typing in a single line of code. It may not be pretty yet, but we'll fix that soon enough.

In the meantime, play around with adding, deleting, and editing recipes. Go ahead; I'll wait for you in the next section.

What Just Happened?

A single line of code, scaffold :recipe, brought everything to life. It let us begin working with our data model. With virtually no work on our part, it created the actions list, show, edit, and delete. It also created default view templates for each of these actions.

Of course, these actions and views are very plain--not the sort of thing you'd want users to see (unless they are total geeks). The good news is that we can leave the scaffolding in place and slowly, one at a time, provide our own versions of the actions and views. Each time you create one of the actions or views it will override the scaffold's version. When you're done, simply remove the scaffold statement from the controller.

Before we do that, did you notice the URLs as you were playing around with your new cookbook? Rails tries very hard to present the user with pretty URLs. Rails URLs are simple and straightforward, not long and cryptic.

Creating Actions and Views

The page that shows the list of all recipes desperately needs improvement. The way to do that is to take over the handling of the list action from the scaffolding.

Edit recipe_controller.rb and add a list method similar to Figure 40.

Figure 40. A new list method

Browse to http://127.0.0.1:3000/recipe/list and you should see something like Figure 41.

Figure 41. The results of the new list method

Because we just created our own definition for the list action, Rails no longer uses the scaffold version. Rails called our list method and then tried to find a view template to render. Because we did not create one, we received this "template missing" error. Let's create our own view template for the list action that only shows each recipe's title and date.

When we created our recipe controller, the generate controller script also created a view directory where we can place the HTML templates that the recipe controller can display. We need to create a template file named list.rhtml in c:\rails\cookbook\app\views\recipe. If you have worked with JSP or ASP pages, this will look familiar. It is simply an html file with Ruby code embedded within <% %> and <%= %> tags.

In the directory c:\rails\cookbook\app\views\recipe, create a file named list.rhtml containing the following:

<html>
<head>
<title>All Recipes</title>
</head>
<body>

<h1>Online Cookbook - All Recipes</h1>
<table border="1">
 <tr>
  <td width="80%"><p align="center"><i><b>Recipe</b></i></td>
  <td width="20%"><p align="center"><i><b>Date</b></i></td>
 </tr>

 <% @recipes.each do |recipe| %>
  <tr>
   <td><%= link_to recipe.title, :action => "show", :id => recipe.id %></td>
   <td><%= recipe.date %></td>
  </tr>
 <% end %>
</table>
<p><%= link_to "Create new recipe", :action => "new" %></p>

</body>
</html>

Edit recipe_controller.rb and add the single line of code shown in Figure 42 to the list method.

Figure 42. Listing all recipes

Refresh your browser and you should see something like Figure 43.

Figure 43. A nicer recipe list

Now this definitely looks better! How does it work?

def list
  @recipes = Recipe.find_all
end

When a user browses to http://127.0.0.1:3000/recipe/list, Rails will call the new list method we just created. The single line of code in the method asks the Recipe class for a collection of all recipes from the database, assigning the collection to the instance variable @recipes.

Next, Rails will look for a template to render and return to the browser. Most of our list template is standard HTML. The real action is in this section of the template:

<% @recipes.each do |recipe| %>
  <tr>
   <td><%= link_to recipe.title, :action => "show", :id => recipe.id %></td>
   <td><%= recipe.date %></td>
  </tr>
 <% end %>

This embedded Ruby code iterates through the collection of recipes retrieved in the controller. The first cell of the table row creates a link to the recipe's show page. Notice the attributes used on the recipe object (title, id, and date). These came directly from the column names in the recipes table.

Adding Categories to the Cookbook

We want to be able to assign a recipe to a category (like "dessert") and be able to list only those recipes that are in a particular category. To do this, we need to add a category table to the database, and a field to the recipe table specifying the category to which the recipe belongs.

In MySQL-Front, create a categories table. Remember to change the automatically created Id field to id, and then create a name field as a varchar(50). The resulting table should look like Figure 44.

Figure 44. The categories table

We also need a category controller and a category model. Open a command window in the cookbook directory and run the commands (Figure 45):

ruby script\generate controller Category
ruby script\generate model Category

Figure 45. Creating the category model and controller

Finally, add scaffolding to the category controller. Edit c:\rails\cookbook\app\controllers\category_controller.rb and add the scaffolding shown in Figure 46.

Figure 46. Category scaffolding

Browse to http://127.0.0.1:3000/category/new and create two categories named Snacks and Beverages. When you are done, you should see something like Figure 47.

Figure 47. A listing of all categories

Assigning a Category to Each Recipe

The cookbook now has recipes and categories, but we still need to tie them together. We want to be able to assign a category to a recipe. To do this we need to add a field to our recipes table to hold the category id for each recipe, and we'll have to write an edit action for recipes that provides a drop-down list of categories.

First, add a category_id field to the recipe table as an int(6) to match the key of the category table. Figure 48 has the details.

Figure 48. The recipe table with its new category_id

This will hold the id of the recipe's category. Now tell the Recipe model class about this too.

Edit c:\rails\cookbook\app\models\recipe.rb and c:\rails\cookbook\app\models\category.rb to add a single line to each model class, as shown in Figures 49 and 50:

Figure 49. Setting relationships in the Recipe model

Figure 50. Setting relationships in the Category model

It should be pretty obvious that this tells Rails that a recipe belongs to a single category and that a category can have many recipes. These declarations actually generate methods to navigate these data relationships in Ruby code.

For example, if I have a recipe object in @recipe, I can find its category name with the code @recipe.category.name. Similarly, if I have a category object in @category, I can fetch a collection of all recipes in that category using the code @category.recipes..

Now it's time to take over the edit recipe action and template from the scaffolding so that we can assign categories. Edit c:\rails\cookbook\app\controllers\recipe_controller.rb and add an edit method like in Figure 51.

Figure 51. The Recipe controller's new edit method

This creates two instance variables that the template will use to render the "edit recipe" page. @recipe is the recipe that we want to edit (the id parameter came in with the web request). @categories is a collection of all the categories in the database. The template will use it to create a drop-down list of category choices.

In the directory c:\rails\cookbook\app\views\recipe, create a file named edit.rhtml that contains the HTML template shown below. It's mostly standard HTML, with the main trick being the <select> and <option> tags that create the drop-down list of categories:

<html>
 <head>
  <title>Edit Recipe</title>
 </head>
 <body>
 <h1>Edit Recipe</h1>

 <form action="../update/<%= @recipe.id %>" method="POST"">
  <input id="recipe_id" name="recipe[id]" size="30" 
         type="hidden" value="<%= @recipe.id %>" />
  <p><b>Title</b><br>
  <input id="recipe_title" name="recipe[title]" size="30" 
         type="text" value="<%= @recipe.title %>" />
  </p>
  <p><b>Description</b><br>
  <input id="recipe_description" name="recipe[description]" 
         size="30" type="text" 
         value="<%= @recipe.description %>" />
  </p>
  <p><b>Category:</b><br>

  <select name="recipe[category_id]">
   <% @categories.each do |category| %>
       <option value="<%= category.id %>" 
         <%= ' selected' if category.id == @recipe.category_id %>>
         <%= category.name %>
       </option>
   <% end %>
  </select></p>

  <p><b>Instructions</b><br>
  <textarea cols="40" id="recipe_instructions" 
            name="recipe[instructions]" 
            rows="20" wrap="virtual">
    <%= @recipe.instructions %>
  </textarea> </p>
  <input type="submit" value="Update" />
 </form>

 <a href="/recipe/show/<%= @recipe.id %>">
   Show
 </a> | 
  <a href="/recipe/list">
  Back 
 </a>

 </body>
</html>

You can see the @recipe and @categories variables being used. Notice the section that loops through all of the categories to create a selection list. Look at the <option> tag and notice how it uses the current category assigned to the recipe being edited as the selected option. Study the template and then try it out.

Browse to http://127.0.0.1:3000/recipe/list and edit the recipe for "Ice Water." Change its category to "Beverages," as shown in Figure 52.

Figure 52. Changing the category for a recipe

Before moving on to the final step, make sure that all recipes in the database have a category. Edit each of them, select a category, and update them. If you don't do this, the next step will give you errors.

Displaying Categories in our List of All Recipes

This is the final step. Modify the list template that we made earlier to display each recipe's category.

Edit the file c:\rails\cookbook\app\views\recipe\list.rhtml to look like this:

<html>
<head>
<title>All Recipes</title>
</head>
<body>

<h1>Online Cookbook - All Recipes</h1>
<table border="1">
 <tr>
  <td width="40%"><p align="center"><i><b>Recipe</b></i></td>
  <td width="20%"><p align="center"><i><b>Category</b></i></td>
  <td width="20%"><p align="center"><i><b>Date</b></i></td>
 </tr>

 <% @recipes.each do |recipe| %>
  <tr>
   <td><%= link_to recipe.title, :action => "show", :id => recipe.id %></td>
   <td><%= recipe.category.name %></td>
   <td><%= recipe.date %></td>
  </tr>
 <% end %>
</table>
<p><%= link_to "Create new recipe", :action => "new" %></p>

</body>
</html>

Now try it by browsing to http://127.0.0.1:3000/recipe/list. You should see something like Figure 53.

Figure 53. Recipes listed with categories

Exercises for the Reader

Congratulations, you've built a Rails web application! Of course, it still needs some work, but it is functional.

Here's some homework for you:

• There is no longer any way to delete a recipe. Add a delete button (or link) to the edit template.
• On the main recipes page, there aren't any links for the pages that let you manipulate categories. Fix that.
• It would be nice to have a way to display only those recipes in a particular category. For example, maybe I'd like to see a list of all snack recipes or a list of all beverage recipes. On the page that lists all recipes, make each category name a link to a page that will display all of the recipes in that category.

Related Reading Programming Ruby The Pragmatic Programmer's Guide, Second Edition By Dave Thomas

This article is the first of a two-part series. Part two will implement the items listed above, but you don't have to wait for me--implementing them yourself could be a fun way to start on Rails development!

Parting Thoughts

Ruby on Rails has taken web application development to a whole new level. You no longer need to do the parts that used to be tedious work, because Rails does them for you. Even if you have to use a legacy database that does not use the Rails naming conventions, you don't have to give up the productivity advantages of using Rails--there is still a way to tell Rails explicitly what table and column names to use.

Now that you've seen firsthand how easy it can be to create a web application, why would you want to do it any other way?

Perhaps your employer has mandated a particular framework or language. You can still take a few days to prototype it in Rails, then go to your boss and say, "I've already finished writing our entire application in Ruby on Rails! If you prefer, we can still take the next few months to write it as we originally planned." <grin>

Editor's note: Want more Ruby on Rails? See Rolling with Ruby on Rails, part 2 and Ajax on Rails.

Resources

Web Sites

• Official Ruby home page
• Official Ruby on Rails home page
• The best way to learn Ruby: read the free book Programming Ruby
• Primary home for open source Ruby projects: RubyForge

Mailing Lists

• Rails mailing list
• Ruby-talk mailing list

Curt Hibbs has been a consultant to well-known companies like Hewlett Packard, Intuit, Corel, WordStar, Charles Schwab, Vivendi Universal, and more. He now works as a Senior Software Engineer for The Boeing Company in St. Louis.

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