TALES root variables

As described, every TALES path: expression must begin with a variable from the current TALES context. Variables may be added to the context one of a number of mechanisms, such as by using tal:define and/or tal:repeat attributes. TALES itself though provides a number of variables of its own - these are the root variables, available to all views:

When using ZPT-Sharp as an ASP.NET MVC ViewEngine, a few additional root variables are provided by the ViewEngine itself.

nothing

The root variable nothing provides a null value. It is a convenient way of getting a null reference.

default

The default root variable provides a special value which indicates that the expression result should indicate the action is to be cancelled.

It is a minimal object implementing CSF.Zpt.Rendering.IActionCanceller which always returns true for the method ShouldCancelAction().

options

options provides access to the keyword options provided to the ZPT rendering process. Keyword options are an IDictionary<string,string> of key/value pairs. For MVC views, this is generally an empty collection as they have no meaning in that environment.

In other rendering scenarios though, it allows the calling process to set a number of variables externally, in order to provide values to the renderer. For example, the command-line page renderer allows setting of keyword options via an optional parameter.

repeat

The repeat root variable provides access to the special repeat variables which expose information about the current iteration. Each repeat variable is available as a child of the repeat root-variable. They are named identically to the local variable created by the tal:repeat attribute.

attrs

The root variable attrs provides access to the original HTML/XML attributes of the element upon which the TALES expression appears. These original attributes are exposed with their values before any manipulation has been performed by TAL.