Help:Parser functions in templates/de

Bei der Anwendung von Parserfunktionen auf Vorlagen-Parametern, kann ein senkrechter Strich ("|") verwendet werden, der immer erscheint, wenn der Parameter bei der Einbindung der Vorlage nicht definiert wird, um einen leeren String als Standardwert bereitzustellen und um anzuzeigen wie die Dinge zu handhaben sind, wenn ein Parameter definiert oder nicht definiert ist.


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 * Beispiel A:  


 * Ergebnis: 


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 * Sample B:  


 * Result: 


 * Comparison

The second usage ( , sample B) with present empty default is often the desired way to handle situations where a parameter exists, but is comprised only of empty space.

One way to test whether a parameter was specified in a template call is thus:

 

In rare cases, a template behaves differently when a parameter is unspecified compared to when it is specified but empty. When this template is used by a wrapper template (which uses the same set of named parameters), one way to ensure undefined parameters remain undefined is as follows (the technique also works with numbered parameters):

Note that the wrapped_template</tt> receives a specified but empty normal_parameter</tt> in two cases: when normal_parameter</tt> is specified and empty, and when normal_parameter</tt> is unspecified (because the default empty value is then specified by the wrapper template).

By contrast, the wrapped_template</tt> receives a specified sensitive_parameter</tt> only when it is indeed specified, because the #if</tt> changes the wrapped_template</tt> parameter name to « sensitive_parameterNULL</tt> » when sensitive_parameter</tt> is undefined.

Note also that wrapped_template</tt> receives a specified and empty sensitive_parameter</tt> only when the wrapper template receives a specified and empty sensitive_parameter</tt>. Of course, one must make sure the suffixed wrapped_template</tt> parameter name is meaningless to the wrapped_template</tt> for this to work properly.