转于：AirZilong的博客

OC是运行时语言，只有在程序运行时，才会去确定对象的类型，并调用类与对象相应的方法。利用runtime机制让我们可以在程序运行时动态修改类、对象中的所有属性、方法，就算是私有方法以及私有属性都是可以动态修改的。本文旨在对runtime的部分特性小试牛刀，更多更全的方法可以参考系统API文件<objc/runtime.h>，demo例子可以参见CSDN的runtime高级编程系列文章。

先看一个Person类：
Person.h

#import <UIKit/UIKit.h>  
  
@interface Person : NSObject  
  
@property (nonatomic,strong) NSString *name;  
  
- (void)sayHello;  
  
@end  ```
Person.m

import "Person.h"

@interface Person()

@property (nonatomic,strong) NSString *address;

@end

@implementation Person

• (instancetype)init
  {
  self = [super init];
  if (self) {
  _address = @"三里屯SOHO";
  self.name = @"AirZilong";
  }
  return self;
  }

• (NSString *)description
  {
  return [NSString stringWithFormat:@"address: %@, name: %@",self.address,self.name];
  }

• (void)sayHello
  {
  NSLog(@"hello ,I'm at %@",self.address);
  }

• (void)interface
  {
  NSLog(@"I'm %@",self.name);
  }
  @end

控制器controller.m

import "ViewController.h"

import "Person.h"

@interface ViewController ()
@end

@implementation ViewController

• (void)viewDidLoad {
  [super viewDidLoad];

Person *onePerson = [[Person alloc] init];  
NSLog(@"first time : %@",[onePerson description]);  
  
#第一步：获取属性列表
unsigned  int count = 0;  
Ivar *members = class_copyIvarList([Person class], &count);  

#第二步：遍历属性  
for (int i = 0; i < count; i++)  
{  
    Ivar var = members[i];
    # 拿到属性  
    const charchar *memberAddress = ivar_getName(var);  
    const charchar *memberType = ivar_getTypeEncoding(var);  
    NSLog(@"address = %s ; type = %s",memberAddress,memberType);  
}  
  
#第三步： 修改私有变量  
Ivar m_address = members[1];  
object_setIvar(onePerson, m_address, @"朝阳公园");  
NSLog(@"second time : %@",[onePerson description]);  
  
  
# 控制私有函数  
[self private];  
//  
//    //添加新方法  
//    [self addFun];  

}

• (void)private
  {

  获取私有方法

  unsigned int count = 0;
  Method *memberFuncs = class_copyMethodList([Person class], &count);
  for (int i = 0; i < count; i++)
  {
  SEL address = method_getName(memberFuncs[i]);
  NSString *methodName = [NSString stringWithCString:sel_getName(address) encoding:NSUTF8StringEncoding];
  NSLog(@"member method : %@",methodName);
  }

} ```

最后打印出来的内容；

**2016-03-17 23:55:20.833 Test-RunTime[6531:98356] first time : address:** **三里屯****SOHO, name: AirZilong**
**2016-03-17 23:55:20.833 Test-RunTime[6531:98356] address = _name ; type = @"NSString"**
**2016-03-17 23:55:20.833 Test-RunTime[6531:98356] address = _address ; type = @"NSString"**
**2016-03-17 23:55:20.833 Test-RunTime[6531:98356] second time : address:** **朝阳公园****, name: AirZilong**
**2016-03-17 23:55:20.833 Test-RunTime[6531:98356] member method : sayHello**
**2016-03-17 23:55:20.834 Test-RunTime[6531:98356] member method : address**
**2016-03-17 23:55:20.834 Test-RunTime[6531:98356] member method : interface**
**2016-03-17 23:55:20.834 Test-RunTime[6531:98356] member method : description**
**2016-03-17 23:55:20.834 Test-RunTime[6531:98356] member method : name**
**2016-03-17 23:55:20.834 Test-RunTime[6531:98356] member method : setName:**
**2016-03-17 23:55:20.834 Test-RunTime[6531:98356] member method : init**
**2016-03-17 23:55:20.834 Test-RunTime[6531:98356] member method : setAddress:**```