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DEVELOPING COLDFUSION 9 APPLICATIONS
Building Blocks of ColdFusion Applications
CFCs support introspection; that is, they can provide information about themselves. If you display a component page
directly in an HTML browser, inspect it in the ColdFusion and Adobe Dreamweaver CS3 component browsers, or use
the CFML
function, you see information about the component. This information includes its path,
GetMetadata
property, methods, and additional information that you can specify using special documentation attributes and tags.
For more information, see
"Using introspection to get information about
When you use a ColdFusion component, you can invoke a method in the CFC. However, typically, you create an
instance of the CFC, and then invoke methods and refer to properties of the CFC.
When to use CFCs
You can use CFCs in the following ways:
• Developing structured, reusable code
• Creating web services
• Creating Flash Remoting elements
• Using asynchronous CFCs
Developing structured, reusable code
CFCs provide an excellent method for developing structured applications that separate display elements from logical
elements and encapsulate database queries. You can use CFCs to create application functionality that you (and others)
can reuse wherever needed, like user-defined functions (UDFs) and custom tags. If you want to modify, add, or remove
component functionality, you make changes in only one component file.
CFCs have several advantages over UDFs and custom tags. These advantages, which CFCs automatically provide,
include all of the following:
• The ability to group related methods into a single component, and to group related components into a package
• Properties that multiple methods can share
• The This scope, a component-specific scope
• Inheritance of component methods and properties from a base component, including the use of the Super keyword
• Access control
• Introspection for CFC methods, properties, and metadata
CFCs have one characteristic that prevents them from being the automatic choice for all code reuse. It takes relatively
more processing time to instantiate a CFC than to process a custom tag. In turn, it takes substantially more time to
process a custom tag than to execute a user-defined function (UDF). However, after a CFC is instantiated, calling a
CFC method has about the same processing overhead as an equivalent UDF. As a result, do not use CFCs in place of
independent, single-purpose custom tags or UDFs. Instead, use CFCs to create bodies of related methods, particularly
methods that share properties.
For more information about UDFs, custom tags, and other ColdFusion code reuse techniques, see
ColdFusion
Elements" on page 146.
Creating web services
ColdFusion can automatically publish CFC methods as web services. To publish a CFC method as a web service, you
specify the
access="remote"
Services Description Language (WSDL) code and exports the CFC methods. For more information on creating web
services in ColdFusion, see
"Using Web
attribute in the method's cffunction tag. ColdFusion generates all the required Web
Services" on page 1093.
Last updated 8/5/2010
components" on page 205.
"Creating
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