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.
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
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.
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 controllers directory and add the
code below to the file.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.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: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/helloOnce 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.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 in 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: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.
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 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: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.
Next, we will modify our
say/hello.cfm view file so that it looks like the
code block bellow. When we do this, the value will be displayed in the browser.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.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.controllers/Say.cfc
component extends="Controller" {
function hello() {
time = Now();
}
function goodbye() {
}
}
Now go to the
views/say directory and create a goodbye.cfm page.Add the following code to the
goodbye.cfm page and save it.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/goodbyeYour browser should look like Figure 5 below:
Figure 5: Your new goodbye action
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.
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: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.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: views/say/goodbye.cfm
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
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.
Last modified 7mo ago