组合一个类并调用它的函数。 如何选择正确的实例？

Question

So Im writing a pygame game and the code is kinda big but I will explain what my problem is. I can also post the code if needed.

So I have a PlayerData class and a EventManager class in pygame, with Python 3.3.2. PlayerData class have 3 methods, self.move_left(self) , self.move_right(self) that changes the position vector depending on the keyboard input, (specificaly x coordinates since it's 2D). The 3rd method is self.update_pos(self) . It takes the position vector, and assign it to the player rect.left/rect.top. The movement functions have a flag parameter, I use it in the EventManager class.

So far this is clear and decent for the player class. Here comes the problem. In my EventManager class I have a for loop that checks for keys pressed/released. In the __init__() I have called self.player = playerData() only. If a key is pressed I call self.player.move_left(flag=True) that is defined in the PlayerData class. If the same key is released i call self.player.move_left(flag=False) , so it stop's subtract pixels to move left.

Again, so far, so good I think. But then I hit the Game Loop, which is like this: Handle events Update game state Draw In the Handle events block, I check for key and if pressed I call the PlayerData method to move. (Means to re-define x,y coordinates of a position Vector defined in the PlayerData class). Then I go to the Update data block, there I call Player.update_pos() , which assigns the new position coordinates to the player rectangle shape. Then I redraw the player.

The problem is the position Vector is not changed when I call the update_pos() method. Here is the code.

import pygame
import sys
import datetime
from pygame.locals import *
from datetime import timedelta

class Vector(object):
    ''' Performs vector aritmetics
    '''
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def add(self, v):
        x = self.x + v.x
        y = self.y + v.y
        return Vector(x, y)


class GroundTerrain(object):
    ''' Ground data structure.
    Creates a ground data structure and her component's.
    '''
    def __init__(self):
        self.position = Vector(0, 334) # TODO: Remove the hard coding
        self.color = (128, 128, 128) # Gray
        self.width = WINDOWWIDTH
        self.height = 166
        self.ground = {'shape': pygame.Rect((self.position.x, self.position.y),
                                        (self.width, self.height)),
                   'color': self.color
                   }

    def draw_ground(self):
        ''' Draw's the ground shape and color using pygame.draw.rect(...).
        '''
        pygame.draw.rect(WINDOWSURFACE, self.ground['color'],
                                    self.ground['shape'])


class PlayerData(object):
    ''' Player data structure.
    Creates a player data structure and handles few actions.
    '''
    def __init__(self):
        self.ground = GroundTerrain()
        self.position = Vector(15, 264) # TODO: Remove the hard coding
        self.size = Vector(50, 70)
        self.velocity = Vector(5, 5)
        self.gravity = Vector(0, -10)

        self.color = (0, 100, 0) # Dark Green
        self.player = {'shape': pygame.Rect((self.position.x, self.position.y),
                                        (self.size.x, self.size.y)),
                   'color': self.color}

    def move_left(self, flag=False):
        ''' Moves the player shape horizontally
        if it's inside window borders.
        '''
        if flag and self.position.x > 0:
            self.position.x = self.position.x - self.velocity.x

    def move_right(self, flag=False):
        ''' Moves the player shape horizontally
        if it's inside window borders.
        '''
        if flag and self.position.x + self.size.x < WINDOWWIDTH:
        self.position.x = self.position.x + self.velocity.x

    def update_pos(self):
        self.player['shape'].left = self.position.x
        self.player['shape'].top = self.position.y

    def draw_player(self):
        ''' Draw's the player shape and color using pygame.draw.rect(...).
        '''
        pygame.draw.rect(WINDOWSURFACE, self.player['color'],
                                    self.player['shape'])


class EventManager(object):
    ''' Handles keyboard event's.
    Toggles player variables according to the event's.
    '''
    def __init__(self):
    self.player = PlayerData()

    def set_variables(self):
        ''' Toggles player variables according to keyboard/mouse event's.
        '''
        for event in pygame.event.get():
            if event.type == QUIT:
                pygame.quit()
                sys.exit()

            if event.type == KEYDOWN:
                if event.key == K_LEFT or event.key == ord('a'):
                    self.player.move_left(True)
                if event.key == K_RIGHT or event.key == ord('d'):
                    self.player.move_right(True)

            if event.type == KEYUP:
                if event.key == K_ESCAPE:
                    pygame.quit()
                    sys.exit()
                if event.key == K_LEFT or event.key == ord('a'):
                    self.player.move_left(False)
                if event.key == K_RIGHT or event.key == ord('d'):
                    self.player.move_right(False)

#-------------------------------------------------------------------------

WINDOWWIDTH = 900
WINDOWHEIGHT = 500
WINDOWSURFACE = pygame.display.set_mode((WINDOWWIDTH, WINDOWHEIGHT), 0, 32)
pygame.display.set_caption('Placeholder')
MAIN_CLOCK = pygame.time.Clock()
FPS = 40

def main():
    pygame.init()
    Ground = GroundTerrain()
    Player = PlayerData()
    EventHandle = EventManager()

    while True:
        # Handle events
        EventHandle.set_variables()

        # Update game state
        Player.update_pos()

        # Draw
        WINDOWSURFACE.fill((0, 0, 0)) # Black
        Ground.draw_ground()
        Player.draw_player()
        pygame.display.update()

        MAIN_CLOCK.tick(FPS)

main()

Answer 1

class EventManager(object):
    ''' Handles keyboard event's.
    Toggles player variables according to the event's.
    '''
    def __init__(self, player):
        self.player = player

    ...

pass the player into the EventManager

    player = PlayerData()
    EventHandle = EventManager(player)