Model Parts, Diagrams, Dictionary Items, and Properties > Properties > Change expression (property)
Change expression (property)
For automation interface information about the Change Expression property, see Event action block (automation interface).
This property specifies the change expression that triggers an Event Action Block whose Trigger Type is Change. This property is available only when the Trigger Type of an Event Action Block is Change.
By default, the Change Expression box is blank.
On a State Diagram, the syntax of an Event Action Block whose Trigger Type is Change is as follows.
when(<change expression>)[<guard condition>]/<action>
You use the Code Editor to edit Change Expression code. For information about the Code Editor, including setting the code language to use, see Overview of the code editor.
This property is set on the Options tab of an Event Action Block's Property Pages. You can click the Edit button and change the code in the Code Editor window. In addition, you can add model object references to the Change Expression code.
On the Property Pages, the Editor button associated with the Change Expression box allows you to change the Change Expression in a text window.
The Change Expression property supports Rich Text, so you can format the text and use model object references.
To change a Change Expression from the State Diagram, right-click the Event Action Block, point to Edit, and then click Trigger.
The following section provides information about the items and diagrams for which Change Expression is a property. For more information about an item or diagram, click it.
Is property of
Event Action Block