I have a template that has an internal property called 'sm' and it has a user defined type. 'sm' has an indirect tag binding to a template parameter 'tagPath' that points to a tag of the same user defined type. 'sm' has an OPC member tag 'Input' of type integer. In the root container of the template I have the following propertyChange event defined:
if event.propertyName == 'sm::Input':
print 'Input changed', event.newValue
When a window containing the template is opened I get the following on the output console:
Input changed None
Input changed 22
Input changed None
Input changed 22
I get the same output on the console each time the window loads even if the value of 'Input' never changes.
If I do the same thing with an internal property of a standard data type I don’t see this behaviour. It seems to only happen with internal properties of user defined type.
This toggling back and forth is causing issues for my event script. Also since 'Input' is an OPC tag this is triggering several writes to the tag in the PLC. Some of which are trying to write a value of None.