Using ColdFusion components

There are two ways to use a CFC:

• You can instantiate a CFC object, which creates a CFC instance. You then invoke the methods of the instance. You can access the CFC methods and data as instance elements. You can also use the instance in the cfinvoke tag to invoke the CFC methods. When you instantiate a CFC, data in the CFC is preserved as long as the CFC instance exists, and ColdFusion does not incur the overhead of creating the instance each time you call a method.

  Instantiate CFCs to preserve data in the CFC. To ensure processing efficiency if you use the CFC more than once on a page, instantiate the CFC before you invoke its methods.

  Methods that are executed remotely through Flash Remoting and web services always create a new instance of the CFC before executing the method.

• You can invoke (call) a method of the CFC without creating an instance of the CFC, which is referred to as transiently invoking a method. In this case, ColdFusion creates an instance of the CFC that exists only from the time you invoke the method until the method returns a result. No data is preserved between invocations and there is no instance of the CFC that you can reuse elsewhere in your CFML. It is considered a best practice to create an instance of a CFC before invoking any of its methods, unless your CFML request uses the CFC only once. If you transiently invoke a method frequently, consider creating a user-defined function to replace the CFC method.

You can create persistent CFCs by assigning the CFC instance to a persistent scope, such as the Session or Application scope. This way, you can create CFCs for objects, such as shopping carts or logged-in users, that must persist for sessions. You can also create CFCs that provide application-specific data and methods.

This section describes how to use CFCs, including the following topics:

• Tags for using CFCs
• CFC invocation techniques
• Instantiating CFCs
• Invoking CFC methods with the cfinvoke tag
• Using components directly in CFScript and CFML
• Invoking CFC methods using forms and URLs
• Accessing CFCs from outside ColdFusion and basic HTML
• Specifying the CFC location

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