将对象从类转换为函数（Pygame）

Question

你们中的一些人可能已经看过我以前有关我目前正在从事的Pygame项目的问题，但是我决定重写并遵循正确的面向对象编程，因为它实际上并没有解决。

这是我到目前为止的内容：

###### Import & Init ######
import pygame
import os, random, math, copy, sys

pygame.init()

###### Variables ######
displayWidth, displayHeight = 600, 600
shipWidth, shipHeight = 50, 50

# Variables that will be used to centre the ship.
startX = displayWidth / 2
startY = displayHeight - 40

screen = pygame.display.set_mode((displayWidth, displayHeight))
pygame.display.set_caption('Space Arcader')

####### Colours #######
# Colour list containing most common colours.
# Colour      R    G    B
red      = (255,   0,   0)
green    = (  0, 255,   0)
blue     = (  0,   0, 255)
grey     = (100, 100, 100)
black    = (  0,   0,   0)
white    = (255, 255, 255)
# Create a list from the colours in order to call it later.
colourList = [red, green, blue, black, white]

####### Classes #######
# Ship class
class Ship(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)

        self.image = pygame.image.load("assets/ship.png").convert_alpha()
        self.image = pygame.transform.scale(self.image,(shipWidth, shipHeight))
        self.transform = self.image

        self.rect = self.image.get_rect()
        self.rect.centerx = startX
        self.rect.centery = startY

        # Where the arrow will be pointing on game start
        self.angle = 90

    def update(self, direction):
        if direction == 'right' and self.angle > 20:
            self.angle -= 4
        elif direction == 'left' and self.angle < 160:
            self.angle += 4

        self.transform = pygame.transform.rotate(self.image, self.angle)
        self.rect = self.transform.get_rect()
        self.rect.centerx = startX
        self.rect.centery = startY

    def draw(self):
        screen.blit(self.transform, self.rect)

# Score class
class Score(object):
    def __init__(self):
        self.total = 0
        self.font = pygame.font.SysFont('Helvetica', 15)
        self.render = self.font.render('Score: ' + str(self.total), True, white)
        self.rect = self.render.get_rect()
        self.rect.left = 5
        self.rect.bottom = displayHeight - 2
        self.render.set_colorkey((0,0,0))

    def update(self, delete_scoreList):
        self.total += ((len(delete_scoreList)) * 50)
        self.render = self.font.render('Score: ' + str(self.total), True, white)

    def draw(self):
        screen.blit(self.render, self.rect)

# Game class
class MainGame(object):
    def __init__(self):
        self.score = 0
        self.game_over = False      

    def controls(self):
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                Menu.terminate()
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    direction = 'left'
                elif event.key == pygame.K_RIGHT:
                    direction = 'right'
            elif event.type == pygame.KEYUP:
                direction = None
                if event.key == pygame.K_SPACE:
                    bullet = Bullet()
                    bullet.rect.x = arrow.rect.x
                    bullet.rect.y = arrow.rect.y
                    all_sprites_list.add(bullet)
                    bulletList.add(bullet)
                elif event.key == pygame.K_ESCAPE:
                    running = False
                    MenuInit()

    def displayInit(self, screen):
        # Set screen width and height.
        display = pygame.display.set_mode((displayWidth, displayHeight))

        # Set the background image of the window.
        background = pygame.image.load("assets/background.jpg")

        # Blit the background onto the screen.
        screen.blit(background, (0, 0))

        # Disable mouse visibility.
        pygame.mouse.set_visible(False)

        # Code to redraw changing/moving objects.
        pygame.display.flip()

# Menu class
class Menu:
    hovered = False
    def __init__(self, text, pos):
        self.text = text
        self.pos = pos
        self.set_rect()
        self.draw()

    def draw(self):
        self.set_rend()
        screen.blit(self.rend, self.rect)

    def set_rend(self):
        menu_font = pygame.font.SysFont('Helvetica', 40)
        self.rend = menu_font.render(self.text, True, self.get_color())

    def get_color(self):
        if self.hovered:
            return (white)
        else:
            return (grey)

    def set_rect(self):
        self.set_rend()
        self.rect = self.rend.get_rect()
        self.rect.topleft = self.pos

    def terminate():
        pygame.quit()
        sys.exit()

####### Functions #######
def MenuInit():
    # Set the background image of the window.
    background = pygame.image.load("assets/menuBackground.jpg")

    options = [Menu("Start game", (200, 250)), Menu("Quit", (265, 300))]

    # Enable mouse visibility.
    pygame.mouse.set_visible(True) 

    while True:       
        for option in options:
            if option.rect.collidepoint(pygame.mouse.get_pos()):
                option.hovered = True
            else:
                option.hovered = False
            option.draw()

        for event in pygame.event.get():
            if event.type == pygame.MOUSEBUTTONDOWN and event.button == 1:
                for option in options:
                    if option.hovered and option.text == "Start game":
                        MainInit()
                    elif option.hovered and option.text == "Quit":
                        Menu.terminate()

        pygame.display.update()
        screen.blit(background,(0,0))

def MainInit():
    # Manage the refresh rate
    clock = pygame.time.Clock()

    # Loop the game until the user closes the application.
    running = True

    # Open an instance of the Game class
    game = MainGame()
    ship = Ship()
    score = Score()

    # Main Loop.
    while running:
        draw = ship.draw()
        ship.update(direction)
#        ship.update(direction)
#        ship.draw()
        controls = game.controls()
        game.displayInit(screen)

        # Refresh rate speed (frames per second).
        clock.tick(60)

# Open the menuInit() function which brings up the main menu.  
if __name__ == '__main__':
    MenuInit()

所以我的问题是试图弄乱飞船并得分到MainInit（）函数上，该函数调用游戏类对象，如上所示。 调用游戏类对象可以正常工作，因为背景图像会更改并且控件可以正常工作。 但是，当我采用相同的方法进行评分时，它似乎不起作用。 在注释掉的注释中，您可以看到我尝试了一些操作，但是遇到了各种错误，例如"NameError: global name 'direction' is not defined"或NameError: global name 'update' is not defined "NameError: global name 'direction' is not defined" NameError: global name 'update' is not defined

有指针吗？ :)

非常感谢你。

Answer 1

问题是由范围外的变量引起的-正是错误告诉您： global name 'direction' is not defined" 。

您可以使用direction在您的def MainInit()但direction是从未在函数定义。 您定义/设置direction可变的位置位于class MainGame.controls() 。

问题是，然而，该direction在-variable创建class MainGame.controls()仅局部的 。 它只会存在于该特定函数MainGame.controls() 。 当不再使用该函数时， direction的值将不复存在-这就是为什么在def MainInit()不存在诸如direction这样的东西的原因。 这超出范围 。

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若要解决此问题，您可以选择将direction用作全局变量。 它要求您在任何功能之外定义direction值，因此一开始就应该起作用。

每当您要读取/修改特定的全局变量时，都应该使用global关键字，以告诉您的Python函数您要使用/修改全局变量，而不是局部变量。

global direction

您可能对此很感兴趣： https : //stackoverflow.com/questions/423379/using-global-variables-in-a-function-other-than-the-one-that-c​​reated-them

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我个人不会使用全局变量，而是将direction成员变量存储在Ship类中并直接对其进行更改。

全局变量可能变得一团糟。