我正在写一个游戏，石头掉下来，你用鼠标让你的厨师不被压碎。当石头从屏幕上掉下来时，另外两块石头会生成并掉落。这种情况一直持续到你的角色被抹掉。
但是我得到了错误：
TypeError: unbound method additonal_drop() must be called with Dropper instance as first argument (got nothing instead)
我不确定我应该在(). 有人可以向我解释这个错误吗？
另外，如何让Dropper精灵不可见？
这是我的代码：
from livewires import games, color
import random
games.init(screen_width = 640, screen_height = 480, fps = 50)
class Chef(games.Sprite):
image = games.load_image("chef.bmp")
def __init__(self):
super(Chef, self).__init__(image = Chef.image,
x = games.mouse.x,
bottom = games.screen.height)
def update(self):
""" Move to mouse x position. """
self.x = games.mouse.x
if self.left < 0:
self.left = 0
if self.right > games.screen.width:
self.right = games.screen.width
self.check()
def check(self):
""" Check if hit by rocks. """
for rock in self.overlapping_sprites:
rock.end_game()
class Rock(games.Sprite):
"""
A rock which falls to the ground.
"""
image = games.load_image("rock.bmp")
speed = 1
def __init__(self, x = 320, y = 90):
""" Initialize a rock object. """
super(Rock, self).__init__(image = Rock.image,
x = x, y = y,
dy = Rock.speed)
def end_game(self):
""" End the game. """
end_message = games.Message(value = "Game Over",
size = 90,
color = color.red,
x = games.screen.width/2,
y = games.screen.height/2,
lifetime = 2 * games.screen.fps,
after_death = games.screen.quit)
games.screen.add(end_message)
def update(self):
""" Check if bottom edge has reached screen bottom. """
if self.bottom > games.screen.height:
self.destroy()
Dropper.additonal_drop()
class Dropper(games.Sprite):
"""
A invisible sprite that drops the rocks.
"""
image = games.load_image("rock.bmp")
def __init__(self, y = 55, speed = 2, odds_change = 200):
""" Initialize the dropper object. """
super(Dropper, self).__init__(image = Dropper.image,
x = games.screen.width / 2, y = y,
dx = speed)
self.odds_change = odds_change
self.time_til_drop = 0
def update(self):
""" Determine if direction needs to be reversed. """
if self.left < 0 or self.right > games.screen.width:
self.dx = -self.dx
elif random.randrange(self.odds_change) == 0:
self.dx = -self.dx
def additonal_drop(self):
new_rock = Rock(x = self.x)
games.screen.add(new_rock)
new_rock = Rock(x = self.x)
games.screen.add(new_rock)
def main():
""" Play the game. """
wall_image = games.load_image("wall.jpg", transparent = False)
games.screen.background = wall_image
the_chef = Chef()
games.screen.add(the_chef)
the_rock = Rock()
games.screen.add(the_rock)
the_dropper = Dropper()
games.screen.add(the_dropper)
games.mouse.is_visible = False
games.screen.event_grab = True
games.screen.mainloop()
# start it up!
main()