Object-Oriented Events for Interactive Fiction

events.py

"""
A short example of my proposed object-oriented event framework for IF games.
Every event should implement a go() method, which calls super().go() before doing
anything else. After that, it should check whether its own go() method is
applicable by making a call to self.should_fire(<EventType>).
"""

class Event:
    """Generic Event type."""
    def __init__(self, obj):
        self.obj = obj  # Event is applied to this object.
        self._interrupt_after = set()  # Set of things to interrupt for.
        self._should_continue = True  # Has our event (not) been interrupted?

    def should_fire(self, current_type):
        """Determine whether we should apply current_type's handler."""
        if not self._should_continue:
            # We've already interrupted; don't handle the event.
            return False
        elif current_type in self._interrupt_after:
            # We need to interrupt now; handle it with this type.
            self._should_continue = False
        return True  # Handle the event with this type.

    def go(self):
        """Override this method if you want your event to do something."""

    def interrupt_after(self, *args):
        """Add an arbitrary list of event types at which we interrupt."""
        for a in args:
            self._interrupt_after.add(a)

        
class Touch(Event):
    """Sent when an object is touched."""
    def go(self):
        super().go()
        if self.should_fire(Touch):
            print(self.obj, "was touched!")

        
class Pull(Touch):
    """Sent when an object is pulled."""
    def go(self):
        super().go()
        if self.should_fire(Pull):
            print(self.obj, "was pulled!")


class LeverPull(Pull):
    """Sent when a lever is pulled."""
    def go(self):
        super().go()
        if self.should_fire(LeverPull):
            print(self.obj, "was lever-pulled!")


class ElectrifiedLeverPull(LeverPull):
    """Sent when an electrified lever is pulled."""
    def go(self):
        self.interrupt_after(Touch)
        super().go()
        if self.should_fire(ElectrifiedLeverPull):
            print(self.obj, "was electric-lever-pulled!")
        print("ZAP!")


class WorkingLever:
    def __str__(self):
        return "Working Lever"


class ElectrifiedLever:
    def __str__(self):
        return "Electrified Lever"

        
LeverPull(WorkingLever()).go()
print()
ElectrifiedLeverPull(ElectrifiedLever()).go()