Pygame：如何多态地编写事件循环

Question

我对pygame有点陌生，在试图回到它的时候，我发现了“用多态性替换你的条件”的建议。大多数 pygame 教程建议使用“for event in pygame.event.get（）”循环，然后使用条件来确定是否发生了任何特定事件。1：如何使用多态函数编写该代码 2：是否值得重构代码，或者只是将条件保持原样以下是大多数教程推荐的内容def gameloop():"""Stuff that comes before the event-loop"""for event in pygame.event.get():    if event.type == pygame.QUIT:   # This is the conditional I want to remove        quit_functions()以下是我想如何做到这一点from abc import ABC, abstractmethodimport pygamedef detect_event(event_class_name):    for event in pygame.event.get():        # This is how I want to get the event and then assign it a function        event_class_name.determine_event(event)# Above: I want to use this function to detect events and call their functions# Below: This is how I want to assign functions to the eventsclass EventHandler(ABC):    @staticmethod    @abstractmethod    def determine_event(event): passclass Exit(EventHandler):    @staticmethod    # How do I identify this with the event-type "pygame.QUIT," for example    def determine_event(event):        pygame.quit()        quit(0)

Answer 1

在 pygame 中，事件类型是枚举器常量。必须将此常量映射到相应的类。使用字典：

def Exit(event):

    # [...]

def Keydown():

    # [...]

eventhandler = {pygame.QUIT: Exit, pygame.KEYDOWN: Keydown}

当然，字典也可以动态生成甚至扩展。（例如：eventhandler[pygame.MOUSEBUTTONDOWN] = MouseDown)

必须将事件委托给在事件处理程序中分配的相应操作：

while True:

    for event in pygame.event.get():

        if event.type in eventhandler:

            eventhandler[event.type](event)

例：

class EventHandler():

    @staticmethod

    def determine_event(event): pass

class Exit(EventHandler):

    @staticmethod

    def determine_event(event):

        pygame.quit()

        quit(0)

class Keydown(EventHandler):

    @staticmethod

    def determine_event(event):

        print(event.key)

eventhandler = {pygame.QUIT: Exit, pygame.KEYDOWN: Keydown}

while True:

    for event in pygame.event.get():

        if event.type in eventhandler:

            eventhandler[event.type].determine_event(event)

对于更通用的方法，可以在列表中管理处理程序。因此，可以将多个操作关联到一个事件类型：

def Exit(event):

    # [...]

def Keydown1():

    # [...]

def Keydown2():

    # [...]

eventhandler = {pygame.QUIT: [Exit], pygame.KEYDOWN: [Keydown1, Keydown2]}

while True:

    for event in pygame.event.get():

        if event.type in eventhandler:

            for target in eventhandler[event.type]:

                target(event)

例：

class EventHandler():

    targets = {}

    @staticmethod

    def add(type, event):

        EventHandler.targets.setdefault(type, []).append(event) 

    @staticmethod

    def notify(event):  

        if event.type in EventHandler.targets:

            for target in EventHandler.targets[event.type]:

                target.determine_event(event)

    @staticmethod

    def determine_event(event): pass

class Exit(EventHandler):

    @staticmethod

    def determine_event(event):

        pygame.quit()

        quit(0)

class KeydownPrint(EventHandler):

    @staticmethod

    def determine_event(event):

        print(event.key)

class KeydownAction(EventHandler):

    @staticmethod

    def determine_event(event):

        print("action")

EventHandler.add(pygame.QUIT, Exit)

EventHandler.add(pygame.KEYDOWN, KeydownPrint)

EventHandler.add(pygame.KEYDOWN, KeydownAction)

while True:

    for event in pygame.event.get():

        EventHandler.notify(event)

或者甚至是两个答案的组合（参见@AKX的答案）：

class EventHandler:

    targets = {}

    def register(type):

        def decorator(fn):

            EventHandler.targets.setdefault(type, []).append(fn)   

        return decorator

    def notify(event):

        fnl = EventHandler.targets[event.type] if event.type in EventHandler.targets else []  

        for fn in fnl: 

          fn(event)

@EventHandler.register(pygame.QUIT)

def onExit(event):

    pygame.quit()

    quit(0)

@EventHandler.register(pygame.KEYDOWN)

def keydownPrint(event):

    print(event.key)

@EventHandler.register(pygame.KEYDOWN)

def keydownAction(event):

    print("action")

while True:

    for event in pygame.event.get():

        EventHandler.notify(event)

Answer 2

你不需要使用带有静态方法的类，并且基于Rabbid76的答案进行构建，一种（恕我直言）优雅的方法是使用装饰器在dict中注册每个事件处理程序：

import pygame

event_handler_registry = {}

def register_event_handler(event):

    def decorator(fn):

        event_handler_registry[event] = fn

        return fn

    return decorator

@register_event_handler(pygame.QUIT)

def on_exit(event):

    pygame.quit()

    quit(0)

@register_event_handler(pygame.KEYDOWN)

def on_key_down(event):

    print(event.key)

while True:

    for event in pygame.event.get():

        event_handler = event_handler_registry.get(event.type)

        if event_handler:

            event_handler(event)

        else:

            print(f"No event handler for {event}")

Answer 3

也许你可以用一个字符串使用eval（）：

EVENTS = {

pygame.QUIT : "quit_handler()" ,

pygame.MOUSEBUTTONDOWN: "click_handler(event)"

}

for event in pygame.event.get:

    eval (EVENTS.get(event.type))