Nocall expression syntax:
nocall_expression ::= 'nocall:' path_expression
Nocall expressions avoid rendering the results of a path expression.
An ordinary path expression tries to render the object that it fetches. This means that if the object is a function, Script, Method, or some other kind of executable thing, then expression will evaluate to the result of calling the object. This is usually what you want, but not always. For example, if you want to put a DTML Document into a variable so that you can refer to its properties, you can't use a normal path expression because it will render the Document into a string.
Using nocall to get the properties of a document:
<span tal:define="doc nocall:here/aDoc"
tal:content="string:${doc/getId}: ${doc/title}">
Id: Title</span>
Using nocall expressions on a functions:
<p tal:define="join nocall:modules/string/join">
This example defines a variable join which is bound to the
string.join function.