As used in our earlier examples, the createObject() function creates and returns a ColdFusion object.

<cfscript>
objGreeting = createObject('component', 'greetings');
</cfscript>

Listing 1.19

Here, we are creating a new instance of the "greetings" component. The first parameter tells the createObject() function that we want a component, and the second references the name of the component of which we want to create an instance.

While the CFC is in the same directory as the calling page, in the previous example, if we had the CFC within a different directory in the webroot, for example, a folder named components; this second parameter would read as follows:

createObject('component', 'components.greetings');

This is because the second parameter is a dot notation representation of the path to the component.

Similar to the createObject() function, the cfobject tag has three attributes.

<cfobject name="greetingsObject" component="greetings" type="component" />

Listing 1.20

The name attribute defines the name of the returned variable of the CFC instance so you can access the component to use your methods. The component attribute represents a dot notation path to the CFC you wish to instantiate. The third attribute, type, is optional, and has the default value component.

The enhancements in ColdFusion 9 now provide an alternative way of creating an instance of a component object without using the createObject() function.

We can now create the object through the use of the new operator, like so:

<cfscript>
// create the object
objGreeting = new greeting();
</cfscript>

Listing 1.21

Let's make a call to our sayHello() method within the greetings.cfc component.

Add the following code to your hello.cfm template page:

<cfinvoke component="greetings" method="sayHello" returnVariable="strHello" />
<cfoutput>#strHello#</cfoutput>

Listing 1.22

Here, we are invoking the greetings component, selecting the method within the CFC that we want to access, (in this case the sayHello() function) and assigning a variable (strHello), to which the returned data will be saved for us to access it within the page.

Outputting the returnVariable onto the page will provide us with the same result as we have seen before.

The cfinvoke tag also allows us to pass in parameters to the methods we are calling, by means of the cfinvokeargument tag.

<cfinvoke component="greetings" method="personalGreeting" returnVariable="strPersonalGreeting">
<cfinvokeargument name="firstName" value="Matt" />
<cfinvokeargument name="lastName" value="James" />
</cfinvoke>

Listing 1.23

We are sending our parameters used in the personalGreeting() method in a similar format to the cfargument tag, using the cfinvokeargument tag, which is nested within the cfinvoke tag. The cfinvokeargument tag takes the name and value of the argument and sends it into the method you are calling.

Alternatively, when using the cfinvoke tag, you can send through the parameters as named attribute-value pairs, providing one attribute per argument.

<cfinvoke component="greetings" method="personalGreeting" firstName="Gary" lastName="Brown" returnVariable="strPersonalGreeting" />

Listing 1.24

You can see in the previous code that the firstName and lastName parameters are written as attributes within the cfinvoke tag itself.

The optional argumentCollection attribute for the cfinvoke tag accepts a structure in the form of an associative array of arguments to pass into the method.

<cfscript>
// create a structure to hold the values
stuArguments = structNew();
stuArguments.firstName = "James";
stuArguments.lastName = "Brown";
</cfscript>
<cfinvoke component="greetings" method="personalGreeting" argumentCollection="#stuArguments#" returnVariable="strPersonalGreeting" />

Listing 1.25

The structure names must match the names of the arguments within the method.