Easy, Powerful Extensibility

In Chapter 22, "Building User-Defined Functions," you learned how to create your own user-defined functions (UDFs). These are exciting because they allow you to add to the CFML language to better suit your needs. Once you have written a UDF, you can use it just like one of ColdFusion's own built-in functions. Extending ColdFusion's language lets you reuse your code in many different places. That makes your job easier and more productiveplus, it's fun!

Let's recap the four basic ways of extending ColdFusion:

• User-Defined Functions. If there is some function that you feel is missing from ColdFusion's list of built-in functions, or that would be handy for an application you're building, you can just make the function yourself.

• Custom Tags. While UDFs allow you to make your own functions, custom tags let you create your own CFML tags. Of all the extensibility methods listed here, custom tags are the most flexible and powerful. The first half of this chapter discusses custom tags.

• ColdFusion Components (CFCs). Conceptually, CFCs are similar to custom tags, but imply a more structured, object-oriented manner of programming. CFCs are also at the heart of ColdFusion MX's Flash and Web Services integration. The second half of this chapter discusses CFCs.

• CFX Tags. It is also possible to write your own CFX tags in either Java or C++. For more information about writing CFX tags, see the ColdFusion documentation or consult this book's companion volume, Advanced Macromedia ColdFusion MX 7 Application Development.