Extensions.EventHandling.MonitorChangeEventSource

Classification

Name	MonitorChangeEventSource
Short Description	Create an event source for change event
Class	Term
Extension	OTX EventHandling extension
Group	Event source related terms
Exceptions	-
Checker Rules	Event_Chk002
Standard Compliant	Yes

OTL Syntax

EventSourceTerm = EventHandling.MonitorChangeEventSource(Variable);

Description

The OTX MonitorChangeEventSource term creates an event source that shall monitor a variable's value and fire an event when it changes. The fired event shall maintain a snapshot of the new value of the monitored variable, which may be read out later (see GetNewValue term). Event queueing shall start immediately once the event source is created.

IMPORTANT — Change-monitoring shall be shallow. This means that changes inside of complex values shall NOT be recognized, like e.g. a change of an item in a List or Map, or the removal of items from a List or Map, etc. Regarding complex data types the only recognized change is when the variable changes its value, e.g. when another List is assigned to the variable.

IMPORTANT — The case when a value is assigned to a formerly uninitialized variable shall also be recognized as a change event and shall NOT pose an error.

Return Value

The Term returns the value, see table below.

In OTX, Terms are categorized according to its return data type!

Data Type	Description
EventSource	The EventSource, the changes in the value of a variable monitored.

Properties

Name	Data Type	Class	Default	Cardinality	Description
Variable	-	Variable	-	[1]	Represents the variable that shall be monitored.

OTL Examples

Boolean Bool1 = false;
EventHandling.EventSource EventSource1;
EventHandling.Event Event1;

EventSource1 = EventHandling.MonitorChangeEventSource(Bool1);

parallel
{
   lane
   {
      Bool1 = true;
   }
   lane
   {
      EventHandling.WaitForEvent({EventSource1}, Event1);
   }
}

See also

ThresholdExceededEventSource
TimerExpiredEventSource