MACROMEDIA ColdFusion MX, Руководство по разработке

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Using custom CFML tags 167
Consider using UDFs in the following circumstances:
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You must pass in a number of arguments, process the results, and return a value. UDFs can
return complex values, including structures that contain multiple simple values.
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You want to provide logical units, such as data manipulation functions.
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Your code must be recursive.
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You distribute your code to others.
If you can create either a UDF or a custom CFML tag for a particular purpose, first consider
creating a UDF because invoking it requires less system overhead than using a custom tag.
For more information
For more information on user-defined functions, see Chapter 10, “Writing and Calling User-
Defined Functions,” on page 191 .
Using custom CFML tags
Custom tags written in CFML behave like ColdFusion tags. They can do all of the following:
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Take arguments.
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Have tag bodies with beginning and ending tags.
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Do specific processing when ColdFusion encounters the beginning tag.
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Do processing that is different from the beginning tag processing when ColdFusion encounters
the ending tag.
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Have any valid ColdFusion page content in their bodies, including both ColdFusion built-in
tags and custom tags (referred to as nested tags), or even JSP tags or JavaScript.
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Be called recursively; that is, a custom tag can, if designed properly, call itself in the tag body.
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Return values to the calling page in a common scope or the calling page’s Variables scope, but
custom tags do not return values directly, the way functions do.