Programming ColdFusion

Returning Data

The caller scope passes data from inside a custom tag back to the calling template. Because custom tags exist within their own scope, you must use the caller scope if you want to make variables you create within your custom tag available to the calling template.

Setting a caller variable is just like setting any other type of ColdFusion variable. You may assign any datatype to a variable in the caller scope. This means that you can pass both simple and complex datatypes from inside a custom tag back to the template that called it.

Let’s create a quick example that demonstrates passing an attribute to a custom tag, acting on that attribute, and passing a variable back using the Caller scope. In Example 19-3, you will find a custom tag called CF_CountWords (save the template as CountWords.cfm on your server). The tag is designed to accept a single attribute called String, count the number of words in the string, and return a caller variable back to the calling template with the number of words in the string. The number of words in the string is calculated by treating the string as a list and using the space character as the delimiter. The ListLen( ) function performs the calculation. Once the number of words is calculated, it is passed back to the calling template as a variable named NumberOfWords.

Example 19-3. Counting the Number of Words in a Block of Text

<CFSETTING ENABLECFOUTPUTONLY="Yes"> <!------------------------------------------------------------------------ ...