Composition 和 Inheritance

Question

"""
这段代码是检查汽车是否启动，其中pump method好像不起作用，要让pressure>0,车子才能启动，应该怎么修改
"""
class Car:
    def __init__(self,VIN,engine,tires):
        self.VIN=VIN
        self.engine=engine
        self.tires=tires
class Tires:
    def __init__(self,size):
        self.size=size
        self.pressure=0
    def get_pressure(self):
        return self.pressure
    def pump(self,psi):
        self.pressure=psi
class Engine:
    def __init__(self,fuel_type):
        self.fuel_type=fuel_type
        self.state='off'
    def start(self):
        self.state = 'on'
    def stop(self):
        self.state = 'off'
    def get_state(self):
        return self.state
city_tires=Tires(15)
off_road_tires=Tires(18)
electric_engine=Engine('electric')
petrol_engine=Engine('petrol')
city_car=Car('111A',electric_engine,city_tires)
all_terrain_car=Car('888S',petrol_engine,off_road_tires)
        
print('All-terrain car engine is', all_terrain_car.engine.get_state())
all_terrain_car.tires.pump(10)
 

all_terrain_car.engine.start()
print('All-terrain car engine is', all_terrain_car.engine.get_state())

all_terrain_car.engine.stop()
print('All-terrain car engine is', all_terrain_car.engine.get_state())

all_terrain_car.engine.start()
print('All-terrain car engine is', all_terrain_car.engine.get_state())
print(all_terrain_car.tires.get_pressure()) 

print('City car engine is', city_car.engine.get_state())

city_car.engine.start()
print('City car engine is', city_car.engine.get_state())

city_car.engine.stop()
print('City car engine is', city_car.engine.get_state())

Answer 1

class Car:
    def __init__(self,VIN,engine,tires):
        self.VIN=VIN
        self.engine=engine
        self.tires=tires
        self.engine.tires=tires#动态给这辆车的引擎添加关联的轮胎，因为要判断胎压，需要在引擎中检查胎压，建立联系
class Tires:
    def __init__(self,size):
        self.size=size
        self.pressure=0
    def get_pressure(self):
        return self.pressure
    def pump(self,psi):
        self.pressure=psi
class Engine:
    def __init__(self,fuel_type):
        self.fuel_type=fuel_type
        self.state='off'
    def start(self):
        if self.tires.pressure>0:#这里获取动态添加的引擎关联的轮胎胎压进行判断
            self.state = 'on'
    def stop(self):
        self.state = 'off'
    def get_state(self):
        return self.state
city_tires=Tires(15)
off_road_tires=Tires(18)

electric_engine=Engine('electric')
petrol_engine=Engine('petrol')

city_car=Car('111A',electric_engine,city_tires)
all_terrain_car=Car('888S',petrol_engine,off_road_tires)
        
print('All-terrain car engine is', all_terrain_car.engine.get_state())
all_terrain_car.tires.pump(10)
 
 
all_terrain_car.engine.start()
print('All-terrain car engine is', all_terrain_car.engine.get_state())
 
all_terrain_car.engine.stop()
print('All-terrain car engine is', all_terrain_car.engine.get_state())
 
all_terrain_car.engine.start()
print('All-terrain car engine is', all_terrain_car.engine.get_state())
print(all_terrain_car.tires.get_pressure()) 
 
print('City car engine is', city_car.engine.get_state())
 
city_car.engine.start()
print('City car engine is', city_car.engine.get_state())
 
city_car.engine.stop()
print('City car engine is', city_car.engine.get_state())