Pygame:如何以多态方式编写事件循环 [英] Pygame: how to write event-loop polymorphically

问题描述

我对 pygame 有点陌生，在尝试重新开始时，我发现了用多态替换条件"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.

I'm some-what new to pygame, and while trying to get back into it, I found the advice "replace your conditionals with polymorphism." Most pygame tutorials recommend using the "for event in pygame.event.get()" loop and then using a conditional to determine if any particular event has occured.

1:如何使用多态函数编写代码2:是否值得重构代码，或者只是保持条件不变

1: How do I write that code using a polymorphic function 2: Is it worth it to re-factor the code, or just leave the conditional as-is

以下是大多数教程推荐的内容

Below is what most tutorials recommend

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()

下面是我想如何处理这个

Below is how I want to approach this

from abc import ABC, abstractmethod
import pygame


def 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 events


class EventHandler(ABC):
    @staticmethod
    @abstractmethod
    def determine_event(event): pass


class Exit(EventHandler):
    @staticmethod
    # How do I identify this with the event-type "pygame.QUIT," for example
    def determine_event(event):
        pygame.quit()
        quit(0)

推荐答案

在 pygame 中，事件类型是一个枚举常量.您必须将此常量映射到相应的类.使用字典:

In pygame the event type is an enumerator constant. You have to map this constant to the corresponding class. Use a dictionary:

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)

Of course, the dictionary can be generated or even extended dynamically, too. (e.g.: eventhandler[pygame.MOUSEBUTTONDOWN] = MouseDown)

必须将事件委托给事件处理程序中分配的适当操作:

The events must be delegated to the appropriate actions assigned in the event handler:

while True:
    for event in pygame.event.get():
        if event.type in eventhandler:
            eventhandler[event.type](event)

示例:

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:

---

For a more general approach, the handlers can be managed in a list. So multiple actions can be associated to an event type:

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)

示例:

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(见@AKX的答案):

---

Or even a combination of both answers (see answer of @AKX):

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)

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