XML Publishing with AxKit

The Template Hash: A Closer Look

Understanding how the template hash works is crucial to the effective use of XPathScript. First, the template hash is a bit magical in that (unlike all other Perl variables you may use in your stylesheet) you need not initialize this hash in your stylesheet. It is declared invisibly during execution by the XPathScript processor. This means that you cannot safely initialize a scalar named $t to the top level of your XPathScript stylesheets without causing a conflict. Second, the template hash really takes the form of a hash of hashes. The names given to the top-level keys define the element names that will be matched when apply_templates( ) is called, and the values for those keys are themselves hashes whose predefined keys determine how the given element will be processed if a match is found. A typical rule takes the following form:

            $t->{<element name>}{<sub-key name>} = $some_value;

element name is the full name (including the namespace prefix) of the element you want to match, and sub-key name is one of eight special keys that the XPathScript processor uses to determine how to build the output for matching cases.

Here are all these special subkeys and their associated behaviors:

pre

The scalar value assigned to this key is added to the output just before the matching element is processed.

post

The value assigned is appended to the output just after the matching element is processed.

prechildren

The scalar value assigned is sent to the output before ...