Expression Rule

The “Expression Rule” filter rule (from MM 2.4) allows the execution of further filter rules to be tied to a condition. A node is created in the rule list that can hold one or at most two further filter rules as child nodes. If the condition is met, the first sub-rule is executed; if it is not met, the second sub-rule is executed — if present (if/else principle).

This filter rule has no independent frontend widget output. The “Only remaining values” option affects which options are displayed in other filter widgets.

See also

Practical examples for the Expression Rule can be found in the cookbook: Expression Filter Rule

Installation

This filter rule is part of metamodels/core and is available without additional packages after the basic MetaModels installation.

Settings when Creating the Filter Rule

Setting	Description
Type	Selection of the filter rule type — here: “Expression Rule”.
Enabled	Enables or disables this filter rule.
Comment	Free text field for describing the purpose of this filter rule.
Expression rule	The condition to be evaluated as an expression. Evaluated at runtime; if the expression returns true, the first sub-rule is executed, otherwise the second (if present).
Only remaining values	Shows only values in other filter widgets for which results still exist after applying this expression rule.

Matching Attributes

The expression rule is not directly attribute-bound. The filter rules used in the sub-rules can reference any attributes.