简单的封装继承多态

//类的声明

#import <Cocoa/Cocoa.h>

@interface Animal : NSObject
-(void)jiao;
-(void)eat;
@end

//类的实现
#import "Animal.h"

@implementation Animal
-(void)jiao
{
    NSLog(@"叫");
}
-(void)eat
{
    NSLog(@"吃");
}
@end

#import "Animal.h"

@interface Cat : Animal
-(void)jiao;
@end




#import "Cat.h"

@implementation Cat
-(void)jiao
{
    NSLog(@"喵喵叫");
}
-(void)eat
{
    NSLog(@"猫吃鱼");
}
@end

#import <Foundation/Foundation.h>
#import "Animal.h"
@interface Weishi : NSObject


-(void)feed:(Animal *) animal;
@end




#import "Weishi.h"

@implementation Weishi
-(void)feed:(Animal *)animal
{
    [animal eat];
}
@end

#import <Foundation/Foundation.h>
#import "Animal.h"
#import "Cat.h"
#import "Dog.h"
#import "Weishi.h"
int main(int argc, const char * argv[]) {
    @autoreleasepool {
       
        id test=[[Animal alloc]init];
        [test jiao];
        
        Animal *test1=[[Cat alloc]init];
        [test1 jiao];
        
        id test2=[[Dog  alloc]init];
        [test2  eat];
        
        id test3=[[Weishi alloc]init];
        [test3 feed:test2];
    
    }
    return 0;
}