不说废话，直接上代码。
首先创建一个Person类。
Person.h

import <Foundation/Foundation.h>

@interface Person : NSObject<NSCoding> //遵循NSCoding协议
//创建几个属性
@property (nonatomic, strong)NSString *name;
@property (nonatomic)int age;
@property (nonatomic, strong)NSString *sex;
@property (nonatomic, strong)NSString *info;
@end

Person.m

import "Person.h"

import <objc/message.h> //一定要导入这个文件

@implementation Person

//分别实现下面这两个方法
//归档

• (void)encodeWithCoder:(NSCoder *)aCoder {
  unsigned int count = 0;
  //获取属性列表
  Ivar *ivars = class_copyIvarList([Person class], &count);
  for(int i= 0; i < count; i++) {
  //取出对应的成员属性
  Ivar ivar = ivars[i];
  //获取属性名称
  const char *name = ivar_getName(ivar);
  NSString *key = [NSString stringWithUTF8String:name];
  //归档
  [aCoder encodeObject:[self valueForKey:key] forKey:key];
  }
  free(ivars);
  }

//解档

• (instancetype)initWithCoder:(NSCoder *)aDecoder {
  if (self = [super init]) {
  unsigned int count = 0;
  Ivar *ivars = class_copyIvarList([Person class], &count);
  for (int i = 0; i < count; i++) {
  Ivar ivar = ivars[i];
  const char *name = ivar_getName(ivar);
  NSString *key = [NSString stringWithUTF8String:name];
  //解档
  id value = [aDecoder decodeObjectForKey:key];
  //为成员属性赋值
  [self setValue:value forKey:key];
  }
  free(ivars);
  }
  return self;
  }
  @end

//在一个控制器中

import "ViewController.h"

import <objc/message.h>

import "Person.h"

@interface ViewController ()

@end

@implementation ViewController

• (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  //Ivar runtime里面 Ivar代表成员变量（成员属性）
  unsigned int count = 0;
  Ivar *ivars = class_copyIvarList([Person class], &count);
  //获取其中一个属性名称
  Ivar ivar = ivars[0];
  const char *name = ivar_getName(ivar);
  NSLog(@"成员属性个数:%d。成员属性名是:%s", count,name);
  }

//下面两个保存和读取方法是storyboard拖拽的

• (IBAction)saveData:(id)sender {
  Person *p = [[Person alloc]init];
  p.name = @"hervey";
  p.age = 18;
  p.info = @"http://www.jianshu.com/u/b0bdd6db3cc8";
  //存储沙盒
  NSString *temp = NSTemporaryDirectory();
  NSString *filePath = [temp stringByAppendingPathComponent:@"hervey.txt"];
  //归档
  [NSKeyedArchiver archiveRootObject:p toFile:filePath];
  NSLog(@"沙盒地址:%@",filePath);
  }

• (IBAction)readData:(id)sender {
  //路径
  NSString *temp = NSTemporaryDirectory();
  NSString *filePath = [temp stringByAppendingPathComponent:@"hervey.txt"];
  //解档
  Person *p = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
  NSLog(@"My name is %@ and age is %d.",p.name, p.age);
  NSLog(@"简书地址:%@",p.info);
  }