Events

Events will notify the implementation that things happened. They are called asynchronously, the result will be ignored.

There are three ways to define events, by creating them in the inherited handler, by setting target objects in the handlers events property and by registering events.

Inherited handler

When working with a inherited class, events can be implemented by creating members with a specific name:

class SampleEquipment(secsgem.gem.GemEquipmentHandler):
    def __init__(self, settings: secsgem.common.Settings):
        super().__init__(settings)

    def _on_event_communicating(self, connection):
        pass

In this example when the hsms connection state changes to selected the _on_event_communicating method will be called.

A generic representation of the function would be:

def _on_event_<event_name>(self, <parameters>):
    pass

To catch all events, the _on_event method can be overridden:

class SampleEquipment(secsgem.gem.GemEquipmentHandler):
    def __init__(self, settings: secsgem.common.Settings):
        super().__init__(settings)

    def _on_event(self, *args):
        pass

Target objects

These methods don’t need to be implemented on the handler itself. Other objects can also be registered using the event member names of the handler. The _on_event_<event_name> and _on_event methods are then searched in that object:

class TestClass:
    def _on_event_communicating(self, connection):
        pass

t = TestClass()

handler.events.targets += t

The event handler can work with more than one target objects.

Registering events

Events can also be registered from outside a class:

def f_communicating(connection):
    pass

handler.events.communicating += f_communicating

To unregister simply remove the member:

handler.events.communicating -= f_communicating