对象在运行时获取其类型的能力称为内省。内省可以有多种方法实现。

判断对象类型

-(BOOL) isKindOfClass: classObj判断是否是这个类或者这个类的子类的实例

新建Person和Teacher类

Person

////  Person.h//  DynamicType////  Created by Michael on 2016/9/27.//  Copyright © 2016年 Michael. All rights reserved.//#import 
    
     @interface Person : NSObject {    NSString *name;}-(void) setName:(NSString*) n;@end////  Person.m//  DynamicType////  Created by Michael on 2016/9/27.//  Copyright © 2016年 Michael. All rights reserved.//#import "Person.h"@implementation Person-(void) setName:(NSString*) n {    name = n;}@end
    

Teacher

////  Teacher.h//  DynamicType////  Created by Michael on 2016/9/27.//  Copyright © 2016年 Michael. All rights reserved.//#import "Person.h"//继承Person@interface Teacher : Person-(void) teach;@end////  Teacher.m//  DynamicType////  Created by Michael on 2016/9/27.//  Copyright © 2016年 Michael. All rights reserved.//#import "Teacher.h"@implementation Teacher-(void) teach {    NSLog(@"%@教数学",name);}@end

isMemberOfClass

Person *person = [[Person alloc] init];Teacher *teaher = [[Teacher alloc] init];      //1.isMemberOfClass判断是否是属于这类的实例，是否跟父类有关系他不管//yesif ([teaher isMemberOfClass:[Teacher class]]) {  NSLog(@"teacher Teacher类的成员");}   //noif ([teaher isMemberOfClass:[Person class]]) {  NSLog(@"teacher Person类的成员");}   //noif ([teaher isMemberOfClass:[NSObject class]]) {  NSLog(@"teacher NSObject类的成员");}

isKindOfClass

//2.isKindOfClass判断是否是其子类//yesif ([teaher isKindOfClass:[Teacher class]]) {  NSLog(@"teacher 是Teacher类或子类");}   //yesif ([teaher isKindOfClass:[Person class]]) {  NSLog(@"teacher 是Person类或子类");}   //yesif ([teaher isKindOfClass:[NSObject class]]) {  NSLog(@"teacher 是NSObject类或子类");}

判断对象方法

-(BOOL) respondsToSelector: selector 判读实例是否有这样方法

respondsToSelector

//3.respondsToSelector判断示例是否有这个方法   if ([teaher respondsToSelector:@selector(setName:)]) {  NSLog(@"有此方法");}   if ([teaher respondsToSelector:@selector(setAge)] == NO) {  NSLog(@"无此方法");}

instancesRespondToSelector

//4.instancesRespondToSelector判断类中是否有该方法，不能用在类的对象   if ([Person instancesRespondToSelector:@selector(setName:)]) {  NSLog(@"Person 有此方法");}   if ([Teacher instancesRespondToSelector:@selector(teach)]) {  NSLog(@"Teacher 有此方法");}   if ([Teacher instancesRespondToSelector:@selector(setName:)]) {  NSLog(@"Teacher 有此方法");  }

Objective-C的id类型

在 Objective-C 中，id类型类似于(void*) ,可以指向任何类的实例。而不需要强制转换。

Teacher *teaher = [[Teacher alloc] init];id t = teaher;  //id指向Teacher类[t setName:@"liuguoquan"];[t teach];