在子类方法中添加[self display]
消息后,+display
我得到一个分段错误。我不明白为什么。在说代码应该无限循环之前请分析整个代码。添加上述消息之前的输出是:
2013-10-15 22:24:30.978 Polymorphism2[657:707] <A1: 0x7fd038c09d00>
2013-10-15 22:24:30.981 Polymorphism2[657:707] <A1: 0x7fd038c09d00>
2013-10-15 22:24:30.981 Polymorphism2[657:707] 10
2013-10-15 22:24:30.982 Polymorphism2[657:707] 60
2013-10-15 22:24:30.982 Polymorphism2[657:707] I'm not multiplying this right now
2013-10-15 22:24:30.983 Polymorphism2[657:707] Superclass!!
还行吧。但是在添加上述消息之后[self display]
,它应该在行前多输出"Superclass!!"
一行。它应该是
2013-10-15 22:24:30.983 Polymorphism2[657:707] Subclass!!.
这是超类的代码
@interface Abc: NSObject
- (void)calculate:(int)x;
- (void)calculate2:(int)x;
+ (void)display;
@end
@implementation Abc
- (void)calculate:(int)x{
NSLog(@"%@",self);
NSLog(@"%d",x);
[self calculate:x];
[self calculate2:x];
}
- (void)calculate2:(int)x{
NSLog(@"%d",x*10);
}
+ (void)display{
[self display];
NSLog(@"Superclass!!");
}
@end
和子类
@implementation A1
- (void)start{
NSLog(@"%@",self);
[super calculate:10];
}
- (void)calculate:(int)x{
NSLog(@"%d",x+50);
}
- (void)calculate2:(int)x{// Overriding
NSLog(@"I'm not multiplying this right now");
}
+ (void)display{
NSLog(@"Subclass");
}
- (void)callClassMethod{
[Abc display];
}
@end
最后,主要
int main(){
A1 *obj= [[A1 alloc] init]; //Subclass object
[obj start];
[obj callClassMethod];
}