Prg2/design patterns 1

This is part of Programming 2 2563

Basic information

• Game Programming Patterns by Robert Nystrom
• Refactoring.Guru

• Patterns covered this week
  • Observer: wikipedia, game programmming patterns
  • Command: wikipedia, game programmming patterns
  • State: wikipedia, game programmming patterns
  • Singleton: wikipedia, game programmming patterns

Codes

Observer Pattern (OO version)

File: gamelib.py

class GameApp(ttk.Frame): 
    def __init__(self, parent, canvas_width=800, canvas_height=500, update_delay=33):
        # ...
        self.on_key_pressed_observers = []
    
    # ...
 
    def register_on_key_pressed_observer(self, observer):
        self.on_key_pressed_observers.append(observer)

    def on_key_pressed(self, event):
        for observer in self.on_key_pressed_observers:
            observer.notify(event)

File: monkeys.py

class MonkeyGame(GameApp):
    class AppObserver:
        def __init__(self, app):
            self.app = app

    class SpeedAdjustmentObserver(AppObserver):
        def notify(self, event):
            app = self.app
            if event.char == '+':
                if app.speed < 10:
                    app.speed += 1
                    app.update_speed_text()
                    
            if event.char == '-':
                if app.speed > 1:
                    app.speed -= 1
                    app.update_speed_text()

    class BananaThrowingObserver(AppObserver):
        def notify(self, event):
            app = self.app
            if event.char == ' ':
                if not app.banana.is_moving:
                    app.banana.set_speed(3 * app.speed, 5 * app.speed)
                    app.banana.reset()
                    app.banana.start()

    # ...
        
    def init_game(self):
        # ...

        self.register_on_key_pressed_observer(MonkeyGame.SpeedAdjustmentObserver(self))
        self.register_on_key_pressed_observer(MonkeyGame.BananaThrowingObserver(self))

Observer Pattern (functions)

File: gamelib.py

class GameApp(ttk.Frame): 
    def __init__(self, parent, canvas_width=800, canvas_height=500, update_delay=33):
        # ...

        self.on_key_pressed_handlers = []

    # ...

    def register_on_key_pressed_handler(self, f):
        self.on_key_pressed_handlers.append(f)

    def on_key_pressed(self, event):
        for f in self.on_key_pressed_handlers:
            f(event)

File: monkeys.py

class MonkeyGame(GameApp):
    def handle_speed_adjustment_key_pressed(self, event):
        if event.char == '+':
            if self.speed < 10:
                self.speed += 1
                self.update_speed_text()
                
        if event.char == '-':
            if self.speed > 1:
                self.speed -= 1
                self.update_speed_text()

    def handle_banana_throwing_key_pressed(self, event):
        if event.char == ' ':
            if not self.banana.is_moving:
                self.banana.set_speed(3 * self.speed, 5 * self.speed)
                self.banana.reset()
                self.banana.start()
    # ...

    def init_game(self):
        # ...

        self.register_on_key_pressed_handler(self.handle_speed_adjustment_key_pressed)
        self.register_on_key_pressed_handler(self.handle_banana_throwing_key_pressed)

Command Pattern

class DotUpdateCommand:
    def __init__(self, dot):
        self.dot = dot

    def excute(self):
        self.old_state = self.dot.get_state()
        self.dot.real_update()        

    def undo(self):
        self.dot.set_state(self.old_state)

class Dot(Sprite):
    def init_element(self):
        self.vx = 0
        self.vy = 0

    def random_speed(self):
        self.vx = 5 * randint(-5,5)
        self.vy = -5 * randint(1,10)

    def bounce(self):
        if (self.x > CANVAS_WIDTH) or (self.x < 0):
            self.vx = -self.vx

        if self.y > CANVAS_HEIGHT:
            self.vy = -0.85 * self.vy

    def real_update(self):
        self.x += self.vx
        self.y += self.vy
        self.vy += GRAVITY

        self.bounce()

    def get_update_command(self):
        return DotUpdateCommand(self)

    def get_state(self):
        return (self.x, self.y, self.vx, self.vy)

    def set_state(self, state):
        self.x, self.y, self.vx, self.vy = state

class FlappyGame(GameApp):
    def create_sprites(self):
        self.dots = []
        for i in range(NUM_BALLS):
            dot = Dot(self, 'images/dot.png', CANVAS_WIDTH // 2, CANVAS_HEIGHT // 2)
            dot.random_speed()

            self.dots.append(dot)
            self.elements.append(dot)

    def init_game(self):
        self.create_sprites()

        self.commands = []
        self.is_reversed = False
        self.cmd_index = 0

    def reverse_update(self):
        current_commands = self.commands[self.cmd_index]

        for c in reversed(current_commands):
            c.undo()

        self.cmd_index -= 1
        if self.cmd_index < 0:
            self.is_reversed = False
            self.commands = []

    def create_update_commands(self):
        new_commands = []
        for dot in self.dots:
            new_commands.append(dot.get_update_command())
        return new_commands

    def pre_update(self):
        if self.is_reversed:
            self.reverse_update()
            return

        new_commands = self.create_update_commands()
        for c in new_commands:
            c.execute()

        self.commands.append(new_commands)
        self.cmd_index = len(self.commands) - 1

    def on_key_pressed(self, event):
        self.is_reversed = True