Contents > Developing ColdFusion MX Applications > Reusing Code in ColdFusion Pages > Using custom CFML tags

Using custom CFML tags

Custom tags written in CFML behave like ColdFusion tags. They can do all of the following:

• Take arguments.
• Have tag bodies with beginning and ending tags.
• Do specific processing when ColdFusion encounters the beginning tag.
• Do processing that is different from the beginning tag processing when ColdFusion encounters the ending tag.
• 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.
• Be called recursively; that is, a custom tag can, if designed properly, call itself in the tag body.
• 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.

Although a custom tag and a ColdFusion page that you include using the cfinclude tag are both ColdFusion pages, they differ in how they are processed. When a page calls a custom tag, it hands processing off to the custom tag page and waits until the custom tag page completes. When the custom tag finishes, it returns processing (and possibly data) to the calling page; the calling page can then complete its processing. The following figure shows how this works. The arrows indicate the flow of ColdFusion processing the pages.

Contents > Developing ColdFusion MX Applications > Reusing Code in ColdFusion Pages > Using custom CFML tags

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