Scene Game Tutorial. Episode 03

stephen

Space Escape Episode 03

The reason im doing this tutorial in episodes instead of all at once is so it can evolve over time so to help the community as best it can. that said we have our first contribution! after the fact of losing standard functionality of classes with python by not using Instances i ran a few tests and found that we can return the built in functionality while maintaining only a single instance by creating a Singleton. Attribution for this Episode goes to @mikael for helping improve quality

main focus this Episode will be converting our EventManager into a singleton.

"The singleton pattern is a design pattern that restricts the instantiation of a class to one object."
we add the magic Dunder method __new__ so we can set our classmethod _instance so we can maintain the singleton status by returning cls._instance if cls._instance is not None to __init__.

class EventManager:
    _instance = None

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
        return cls._instance
    
    def __init__(self, *arg, **kwargs):
        self.main=None
        self.hud=None
        self.game_state=None
    
    def start(self, main, hud):
        self.main=main
        self.hud=hud
        self.game_state=GameState.MAIN_MENU
        self.main.view.hidden=True
        self.hud.add_subview(MainMenu())
        
    def update(self, dt):
        pass

    def touch_began(self, touch):
        pass

    def touch_moved(self, touch):
        pass
  
    def touch_ended(self, touch):
        pass

In Main we grab a refernce to EventManager from HUD

class Main(Scene):
    def setup(self):
        self.event_manager=self.view.superview.event_manager
        
    def did_change_size(self):
        pass

    def update(self):
        self.event_manager.update(self.dt)

    def touch_began(self, touch):
        self.event_manager.touch_began(touch)

    def touch_moved(self, touch):
        self.event_manager.touch_moved(touch)

    def touch_ended(self, touch):
        self.event_manager.touch_ended(touch)

Inside HUD lets ceate our initial instance of EventManager since this is our Top Level Object. then after setting our SceneView we call start for HUD.event_manager.start which main and hud inside HUD.event_manager and set our game state andin turn present our main menu.


class HUD(ui.View):
    def __init__(self, *args, **kwargs):
        self.background_color='#66492a'
        
        self.event_manager=EventManager()
        
        # Game Window
        self.main = SceneView(
                scene=Main(), frame=(5, 5, Screen.x-10, Screen.y-10),
                anti_alias=True, frame_interval=1,
                shows_fps=True, background_color='#2c00ff')
        self.add_subview(self.main)
        self.event_manager.start(self.main.scene, self)

We will call it here for this one and it wont feel like we did anything but in the long run this Episode will help our project 10-fold.

Seb

Just wanted to say as a complete beginner this is really helpful! I look forward to the next episode :)

stephen

@Seb said:

Just wanted to say as a complete beginner this is really helpful! I look forward to the next episode :)

Most Excellent!

@karina @mikael @cvp and others lol

I do appollogise for the quite long delay. I was spending time wih my kids that i hadnt seen in little over a year!

I will now continue this tutorial after i go through all my notes and scripts and get back up to speed. there may be a couple changes to the current episodes but it shouldn't be much and it will be to make is series much easier to follow for anyone having troubles.

🙋🏼‍♂️

cvp

@stephen said:

I was spending time wih my kids

Very good idea 😉