The Structure expression syntax

A TALES structure expression may be used to indicate that an expression value should be treated as markup/structure when used with a TAL content or replace attribute, even if that attribute does not use the structure keyword to enable processing of markup.

The syntax of the expression is as follows, it simply prefixes another expression, typically a path expression but it doesn't need to be:

structure:other_expression

Structure expressions must be explicitly activated

Whilst support for structure expressions is included in the main ZptSharp NuGet package, they are not one of the standard expression types. Structure expressions must be explicitly activated using the method AddZptStructureExpressions() before they may be used.

The expression result is wrapped

The result of a structure expression is the result of the 'inner' expression, wrapped within an instance of StructuredMarkupObjectAdapter. This object implements the interface IGetsStructuredMarkup and so content or replace attributes operating upon this value will treat it as structure, without needing the structure keyword.

Use with caution

The same advice as for using the structure keyword with a content or replace attribute goes for using structure expressions. Designers should be vigilent that they do not allow untrusted content to be written to the output unless it has been thoroughly sanitized first.

The structure keyword (for content & replace attributes) is a generally a better solution than the use of structure expressions; it forces designers to be explicit when they want markup to be interpreted as such, and at the point where it is written.

Example

The result of the path expression here/iAmMarkup will be rendered to the output as markup without escaping.

<p tal:define="theMarkup structure:here/iAmMarkup" tal:content="theMarkup">This will be replaced</p>