对象/类混淆？

Question

我注意到今天在玩“init”时，下面的两个对象都会向控制台输出相同的消息“_init：TireSnow”。任何人都可以解释为什么会发生这种情况吗？

// INTERFACE
@interface TireBasic : NSObject {
}
@end

@interface TireSnow : TireBasic {
}
@end
// IMPLEMENT
@implementation TireBasic
- (id) init {
    self = [super init];
    if(self) {
        NSLog(@"TB_init: %@", NSStringFromClass([self class]));
    }
    return self;
}
- (NSString *) description {
return @"This is a BASIC TIRE.";
}
@end

@implementation TireSnow
- (id) init {
    self = [super init];
    if(self) {
        NSLog(@"TS_init: %@", NSStringFromClass([self class]));
    }
    return self;
}
- (NSString *) description {
return @"This is a SNOW TIRE.";
}

@end

EDIT2 - 添加了所有main（）

#import <Foundation/Foundation.h>
#import "CarParts.h"

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    int tireCount;
    CarClass *newCar_001;
    EngineClass *newEngine_001;
    TireBasic *newTire_BASIC;
    TireSnow  *newTire_SNOW;

    // Setup
    NSLog(@"COMPOSITION Start");
    newCar_001 = [[CarClass alloc] init];

    // Engine
    newEngine_001 = [[EngineClass alloc] init];
    [newCar_001 setEngine: newEngine_001];

    // TIRES (BASIC)
    for(tireCount=0; tireCount<2; tireCount++) {
        newTire_BASIC = [[TireBasic alloc] init];
        [newCar_001 setTire:newTire_BASIC];
        [newTire_BASIC release];
    }
    // TIRES (SNOW)
    for(tireCount=0; tireCount<2; tireCount++) {
        newTire_SNOW = [[TireSnow alloc] init];
        [newCar_001 setTire:newTire_SNOW];
        [newTire_SNOW release];
    }
    // Display
    [newCar_001 printCar];

    // Clean up
    [newCar_001 release];
    [newEngine_001 release];
    [pool drain];
    return 0;
}

输出

> COMPOSITION Start
> _init: CarClass
> _init: EngineClass
> TB_init: TireBasic
> TB_init: TireBasic
> TB_init: TireSnow *****
> TS_init: TireSnow
> TB_init: TireSnow *****
> TS_init: TireSnow
>  
> This is a BASIC TIRE.
> This is a BASIC TIRE.
> This is a SNOW TIRE.
> This is a SNOW TIRE.
> 
> _deal: CarClass
> TB_deal: TireBasic
> TB_deal: TireBasic
> TS_deal: TireSnow
> TB_deal: TireSnow ******
> TS_deal: TireSnow
> TB_deal: TireSnow ******
> _deal: EngineClass

带有星星的线来自TireSnow [super init]和[super dealloc]，似乎每次都返回“TireSnow”的[自我类]，有人可以解释为什么吗？

非常感谢

加里

Answer 1

> TS_deal: TireSnow
> TB_deal: TireSnow

你问为什么 TireSnow 打印两次？

先运行[TireBasic init]，然后[TireSnow init]。在这两种情况下，他们都会打印类名，在这两种情况下，类名都是TireSnow。

换句话说，[self class]将始终返回相同的对象，无论它在哪个方法中执行。

Answer 2

TireSnow将在TireBasic init中将其类记录两次，一次在TireSnow init中，一次从super调用到。

只是为了检查：你是否可能会混淆来自TireSnow的两个日志来自TireBasic和TireSnow？

Answer 3

我们能看到你的[[_____ alloc] init]声明吗？我看不出怎么样

[[TireSnow alloc] init]和[[TireBasic alloc] init]将返回相同的内容。好吧，也许如果：

TireSnow  *tire;

tire = (TireSnow *) [TireBasic alloc];
tire = [tire init];