SubscriptionAddCallback
Adds a function callback to a tag subscription. When the value change for a subscribed tag is detected, a callback function can be called. This implements change based Cicode and avoids continuously polling a tag value to monitor changes.
Multiple callbacks are possible to the same subscription.
To remove a callback from a subscription use the SubscriptionRemoveCallback function.
Syntax
SubscriptionAddCallback(iHandle, sCallback)
iHandle
Integer handle of the subscription to add a callback to.
sCallback
String stating the name of a function to call when the value is updated. The function should have the structure:
FUNCTION evtHandler(INT subsHandle)
..
End
Where subsHandle is the subscription that raised the event.
Return Value
0 (zero) if successful, otherwise an error is returned.
Related Functions
TagSubscribe, TagUnsubscribe, SubscriptionGetAttribute, SubscriptionRemoveCallback
See Also