OC多态使用注意

#import <Foundation/Foundation.h>

@interface Animal :NSObject

-(void)eat;

@end

@implementation Animal

-(void)eat{

   NSLog(@"吃东西");

}

@end

@interface Dog : Animal

-(void)eat;

@end

@implementation Dog

-(void)eat{

    NSLog(@"Dog吃东西");

}

@end

@interface Cat : Animal

-(void)eat;

@end

@implementation Cat

-(void)eat{

    NSLog(@"Cat-吃东西");

}

@end

int main(){

    

    NSString *s=[Catnew];//不会报错，oc的弱语法

    

    //多种形态

   Dog *d=[Dognew];//Dog类型

   NSObject *n=[Dognew];

    

    //多态：父类指针指向子类对象

   Animal *a=[Dognew];

    

    [deat];

    //[n eat];

    [a eat];//调用方法时检测对象的真实形象

   return 0;

}