Beginner Tutorial: Hello World

In this tutorial, we'll be writing a simple application to make sure we have CFWheels installed properly and that everything is working as it should.

Testing Your Install

Let's make sure we're all on the same page. I'm going to assume that you've followed the Getting Started guide and have CommandBox all setup. If you haven't done that, stop and read that guide get everything setup. It's okay, this web page will wait for you.

Okay, so you have CFWheels installed and can see the CFWheels "Congratulations!" page as shown below. That wasn't that hard now, was it?

Figure 1: Wheels congratulations screen

Hello World: Your First CFWheels App

Okay, let's get to some example code. We know that you've been dying to get your hands on some code!

To continue with Programming Tutorial Tradition, we'll create the ubiquitous Hello World! application. But to keep things interesting, let's add a little CFWheels magic along the way.

Setting up the Controller

Let's create a controller from scratch to illustrate how easy it is to set up a controller and plug it into the CFWheels framework.

First, create a file called Say.cfc in the app/controllers directory and add the code below to the file.

app/controllers/Say.cfc

component extends="Controller"{
}

Congratulations, you just created your first CFWheels controller! What does this controller do, you might ask? Well, to be honest, not much. It has no methods defined, so it doesn't add any new functionality to our application. But because it extends the base Controller component, it inherits quite a bit of powerful functionality and is now tied into our CFWheels application.

So what happens if we try to call our new controller right now? Lets take a look. Open your browser and point your browser to the new controller. Because my local server is installed on port 60000, my URL is http://127.0.0.1:60000/say. You may need to enter a different URL, depending on how your web server is configured. In my case, I'm using CommandBox.

Figure 2: Wheels error after setting up your blank say controller

The error says "Could not find the view page for the 'index' action in the 'say' controller." Where did "index" come from? The URL we typed in only specified a controller name but no action. When an action is not specified in the URL, CFWheels assumes that we want the default action. Out of the box, the default action in CFWheels is set to index. So in our example, CFWheels tried to find the index action within the say controller, and it threw an error because it couldn't find its view page.

Setting up an Action

But let's jump ahead. Now that we have the controller created, let's add an action to it called hello. Change your say controller so it looks like the code block below:

app/controllers/Say.cfc

component extends="Controller" {
    function hello() {
    }
}

As you can see, we created an empty method named hello.

Now let's call our new action in the browser and see what we get. To call the hello action, we simply add /hello to the end of the previous URL that we used to call our say controller:

http://127.0.0.1:60000/say/hello

Once again, we get a ColdFusion error. Although we have created the controller and added the hello action to it, we haven't created the view.

Setting up the View

By default, when an action is called, CFWheels will look for a view file with the same name as the action. It then hands off the processing to the view to display the user interface. In our case, CFWheels tried to find a view file for our say/hello action and couldn't find one.

Let's remedy the situation and create a view file. View files are simple CFML pages that handle the output of our application. In most cases, views will return HTML code to the browser. By default, the view files will have the same name as our controller actions and will be grouped into a directory under the view directory. This new directory will have the same name as our controller.

Find the views directory inside the app directory, located at the root of your CFWheels installation. There will be a few directories in there already. For now, we need to create a new directory in the views directory called say. This is the same name as the controller that we created above.

Now inside the say directory, create a file called hello.cfm. In the hello.cfm file, add the following line of code:

app/views/say/hello.cfm

<h1>Hello World!</h>

Save your hello.cfm file, and let's call our say/hello action once again. You have your first working CFWheels page if your browser looks like Figure 3 below.

Figure 3: Your first working CFWheels action.

You have just created your first functional CFWheels page, albeit it is a very simple one. Pat yourself on the back, go grab a snack, and when you're ready, let's go on and extend the functionality of our Hello World! application a little more.

Adding Dynamic Content to Your View

We will add some simple dynamic content to our hello action and add a second action to the application. We'll then use some CFWheels code to tie the 2 actions together. Let's get get to it!

The Dynamic Content

The first thing we are going to do is to add some dynamic content to our say/hello action. Modify your say controller so it looks like the code block below:

app/controllers/Say.cfc

component extends="Controller" {
    function hello() {
        time = Now();
    }
}

All we are doing here is creating a variable called time and setting its value to the current server time using the basic ColdFusion Now() function. When we do this, the variable becomes immediately available to our view code.

Why not just set up this value directly in the view? If you think about it, maybe the logic behind the value of time may eventually change. What if eventually we want to display its value based on the user's time zone? What if later we decide to pull it from a web service instead? Remember, the controller is supposed to coordinate all of the data and business logic, not the view.

Displaying the Dynamic Content

Next, we will modify our say/hello.cfm view file so that it looks like the code block below. When we do this, the value will be displayed in the browser.

app/views/say/hello.cfm

<h1>Hello World!</h1>
<p>Current time: <cfoutput>#time#</cfoutput></p>

call your say/hello action again in your browser. Your browser should look like Figure 4 below.

Figure 4: Hello World with the current date and time

This simple example showed that any dynamic content created in a controller action is available to the corresponding view file. In our application, we created a time variable in the say/hello controller action and display that variable in our say/hello.cfm view file.

Adding a Second Action: Goodbye

Now we will expand the functionality of our application once again by adding a second action to our say controller. If you feel adventurous, go ahead and add a goodbye action to the say controller on your own, then create a goodbye.cfm view file that displays a "Goodbye" message to the user. If you're not feeling that adventurous, we'll quickly go step by step.

First, modify the the say controller file so that it looks like the code block below.

app/controllers/Say.cfc

component extends="Controller" {
    function hello() {
        time = Now();
    }

    function goodbye() {
    }
}

Now go to the app/views/say directory and create a goodbye.cfm page.

Add the following code to the goodbye.cfm page and save it.

app/views/say/goodbye.cfm

Goodbye World!

If we did everything right, we should be able to call the new say/goodbye action using the following URL:

http://127.0.0.1:60000/say/goodbye

Your browser should look like Figure 5 below:

Figure 5: Your new goodbye action

Linking to Other Actions

Now let's link our two actions together. We will do this by adding a link to the bottom of each page so that it calls the other page.

Linking Hello to Goodbye

Open the say/hello.cfm view file. We are going to add a line of code to the end of this file so our say/hello.cfm view file looks like the code block below:

app/views/say/hello.cfm

<h1>Hello World!</h1>
<p>Current time: <cfoutput>#time#</cfoutput></p>
<p>Time to say <cfoutput>#linkTo(text="goodbye", action="goodbye")#?</cfoutput></p>

The linkTo() function is a built-in CFWheels function. In this case, we are passing 2 named parameters to it. The first parameter, text, is the text that will be displayed in the hyperlink. The second parameter, action, defines the action to point the link to. By using this built-in function, your application's main URL may change, and even controllers and actions may get shifted around, but you won't suffer from the dreaded dead link. CFWheels will always create a valid link for you as long as you configure it correctly when you make infrastructure changes to your application.

Once you have added the additional line of code to the end of the say/hello.cfm view file, save your file and call the say/hello action from your browser. Your browser should look like Figure 6 below.

Figure 6: Your say/hello action with a link to the goodbye action

You can see that CFWheels created a link for us and added an appropriate URL for the say/goodbye action to the link.

Linking Goodbye to Hello

Let's complete our little app and add a corresponding link to the bottom of our say/goodbye.cfm view page.

Open your say/goodbye.cfm view page and modify it so it looks like the code block below.

CFML: app/views/say/goodbye.cfm

app/views/say/goodbye.cfm

<h1>Goodbye World!</h1>
<p>Time to say <cfoutput>#linkTo(text="hello", action="hello")#?</cfoutput></p>

If you now call the say/goodbye action in your browser, your browser should look like Figure 7 below.

Figure 7: Your say/goodbye action with a link to the hello action

Much More to Learn

You now know enough to be dangerous with CFWheels. Look out! But there are many more powerful features to cover. You may have noticed that we haven't even talked about the M in MVC.

No worries. We will get there. And we think you will enjoy it.