ColdFusion Components (CFCs) serve as the basis for object-oriented programming (OOP) in CFML. This CFC Primer was created to give developers some background and history of the CFML language from the standpoint of enabling modular application development. The primer also intends to introduce developers to the power of CFCs and why it is important to take advantage of CFCs in building applications.
CFCs are CFML's version of objects. Although CFCs are technically not as powerful as Java objects, CFCs also eliminate much of the complexity and strictness of Java while providing almost complete OO functionality. CFML is not a fully object-oriented language. CFCs allow CFML developers, however, to build OO applications that architecturally resemble OO applications in Java and other languages that are completely object-oriented.
CFML developers can use CFCS to build tiered applications in which presentation logic and business logic are completely separate from each another. This separation of presentation and business logic helps developers create applications that are easier to build and maintain.
The following discussion explains the evolution of modular development in CFML, the precursors of CFCs, and the significance of CFCs in giving CFML developers the power to create modular applications.
cfinclude allows developers to write bits of code in CFML templates that can be included anywhere within an application. While cfinclude is not very powerful for writing modular code, it avoids the need to cut and paste common code within an application. Using cfinclude, a piece of functionality contained in an included template can easily be revised in a single place, and these changes will immediately be reflected in every instance of the included CFML template throughout an application. Although cfinclude makes code reusable in a very basic sense, it does not allow for the development of modular, tiered applications in which presentation logic and business logic are truly separated.
Custom tags allow developers to customize CFML code that can be called in similar fashion to built-in CFML tags (e.g. <cf_mytag>). They represent a significant advancement over cfinclude. Custom tags have their own scope and multiple execution modes (start, body, and end), they are powerful tools for encapsulating CFML code in a reusable, easy-to-use construct. Custom tags added considerable modular development capabilities to CFML, but it is still rather difficult to develop fully modular applications by using only custom tags.
User-Defined Functions (UDFs)
User-defined functions (UDFs) allow CFML developers to write customized functionality that is more flexible and more discrete than functionality created with custom tags. While UDFs are not as powerful as custom tags in one respect, UDFs are more useful for smaller bits of functionality or logic and have less performance overhead than custom tags. UDFs can be written within a cfscript block.
CFCs allow CFML developers to create self-contained modular software components that include both functions in the form of UDFs (called methods in many other OO languages) as well as object data. The CFML language became much more powerful with the addition of CFCs, because for the first time it became possible to develop fully modular CFML applications. Many CFML developers are still learning how to take advantage of this capability. By combining UDFs with object-specific data in the form of a CFC, it is now possible to build truly modular, tiered, OO applications in CFML.
The combination of behavior (functions) and attributes (data) within a single object allows CFML developers to model real-world objects as software components. Therefore, now it is much easier to conceptualize and develop complex applications in CFML than it was in the past. In addition, CFCs allow developers to create objects that are cohesive (single-purposed) and loosely coupled to other CFCs within an application, which makes applications much more flexible and easier to maintain.
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