Events

TL;DR - Specify expression / function that must be true, else exception

Events are callouts to Python functions, supplying logic_row as a argument. Events provide extensibility, to address non-database logic (e.g., sending email and messages), and for complex logic that cannot be addressed in rules.

 

Defining Events

To define events, you must declare and implement them, as described below.

 

Declare Event Rule

Declare the event, identifying the class and function to call:

Rule.commit_row_event(on_class=models.Order, calling=congratulate_sales_rep)

 

Implement Python Function

Implement the Python function that handles the event, accepting the supplied arguments:

 

Event Types

There are multiple event types so that you can control how your logic executes within the rule engine.

 

early_row_event

These operate before your derivation / constraint logic executes for each row. So, for example, derivations have not been performed.

 

early_row_event_all_classes

These operate before your logic executes for each row for any class. It is an excellent way to implement generic logic such as time/date stamping. It is also used by the system to activate optimistic locking logic, as shown below.

def handle_all(logic_row: LogicRow):  # OPTIMISTIC LOCKING, [TIME / DATE STAMPING]
        """
        This is generic - executed for all classes.

        Invokes optimistic locking.

        You can optionally do time and date stamping here, as shown below.

        Args:
                logic_row (LogicRow): from LogicBank - old/new row, state
        """
        if logic_row.is_updated() and logic_row.old_row is not None and logic_row.nest_level == 0:
                opt_locking.opt_lock_patch(logic_row=logic_row)
        enable_creation_stamping = True  # CreatedOn time stamping
        if enable_creation_stamping:
                row = logic_row.row
                if logic_row.ins_upd_dlt == "ins" and hasattr(row, "CreatedOn"):
                row.CreatedOn = datetime.datetime.now()
                logic_row.log("early_row_event_all_classes - handle_all sets 'Created_on"'')

Rule.early_row_event_all_classes(early_row_event_all_classes=handle_all)

 

row_event

These operate after your derivation / constraint logic executes for each row. So, for example, derivations have been performed.

 

commit_row_event

These operate after logic executes for all rows. So, for example, sums and counts have been computed.