Class __nullable NSClassFromString(NSString *aClassName);
-(BOOL)isKindOfClass:(Class)aClass;
-(BOOL)isMemberOfClass:(Class)aClass;

//通过这样的方式获取class
Class name = NSClassFromString(@"Student");  
Student *stu = [[name alloc] init]; 

//判断是否为其子类的对象
Student *stu = [[Student alloc]init];  
if([stu isKindOfClass:[Person class]]){  
    NSLog(@"stu是Person类型或其子类");  
}else{  
    NSLog(@"stu不是Person类型或其子类");  
}  
//判断是否是该class的对象
if([stu isMemberOfClass:[Person class]]){  
    NSLog(@"stu是Person类型");  
}else{  
    NSLog(@"stu不是Person类型");  
}  

- (BOOL)respondsToSelector:(SEL)aSelector  判断类型或对象有没有某个方法
+ (BOOL)instancesRespondToSelector:(SEL)aSelector; //判断静态方法

- (id)performSelector:(SEL)aSelector  动态调用对象的方法
- (BOOL)conformsToProtocol:(Protocol *)aProtocol; 判断对象是否实现某个Protocol协议

//动态生成方法选择器
SEL sel =  NSSelectorFromString(@"setAge:");  

//检测是否存在某方法
Student *stu = [[Student alloc]init];  
if([stu respondsToSelector:@selector(setAge)]){  
    NSLog(@"stu 有setAge这个方法");  
}else{  
    NSLog(@"没有");  
}  

//动态动用方法
Student *stu = [[Student alloc]initAge:1];  
int age = [stu performSelector:@selector(age)];  
NSLog(@"%i",age);//输出1  

//动态调用有参数的方法
[stu  performSelector:@selector(setAge1:) withObject:@"2"];  

Persion *persion =  [ [Persion alloc] init ];
//不使用KVC
persion.name = @"shen" ;
//使用KVC的写法
[persion  setValue:@"shen" forKey:@"name"];

//不使用KVC
Persion *persion =  [ [Persion alloc] init ];
Phone *phone = persion.phone;
Battery *battery = phone.battery;

//使用KVC
Battery *battery = [persion valueForKeyPath: @"phone.battery" ];

[persion setValue:[NSNumber numberWithInteger:1] forKey:@"name"]; 
// 编译并运行，但报错

persion.name = [NSNumber numberWithInteger:1]; 
// 不能编译