Module null 

The null datamodel (W3C SCXML B.1) and the registry helpers that make it always available.

Structs

NullDatamodel

The null datamodel: no data, and only In('id') conditions. Every other condition, value expression, assignment, script and foreach is an evaluation error. Inline content (of <content>) is not an expression and is passed through as a string.

NullRegistry

A registry with only the null datamodel.

WithNull

Wraps a host registry so that null is always available.

Constants

NULL_DATAMODEL

The name of the null datamodel.

Functions

create_datamodel

Create the datamodel a chart names (null when it names none) from the host’s registry, or fail with StartError::UnsupportedDatamodel. null is available even when the registry does not list it.

create_datamodel_for

Create the datamodel for chart from the host’s registry through DatamodelRegistry::create_for, so a datamodel that checks charts statically gets the whole chart: StartError::ChartRefused when it refuses the chart, and otherwise as create_datamodel (null when the chart names none, null always available, StartError::UnsupportedDatamodel for an unregistered name).

parse_in_predicate

Parse In('id') or In("id") (surrounding whitespace allowed) and return id.

start_with_registry

Select the chart’s datamodel from the registry and start a session with it. Returns the outcome and the datamodel instance the session must keep using.