原理：将自定义对象归档成data后，利用NSUserDefaults写入本地

一、保存对象

1、归档对象

需要实现NSCoding协议，参考//www.greatytc.com/p/02da153d3583 继承Model类即可

    //首先，要建立一个集成Model对象或者实现NSCoding协议的对象
     Student *student = [[Student alloc] init];
    //下面进行的是对student对象的 name ， studentNumber ，sex 的赋值
    student.name = @"刘德华";
    student.studentNumber = @"2313213";
    student.sex = @"男";
 NSData *data = [NSKeyedArchiver archivedDataWithRootObject:student];  

2、将对象写入本地

利用NSUserDefaults或者封装的HXBSaveTool类(//www.greatytc.com/p/ac273e44bd7c 代码解释)
方法1== NSUserDefaults

  NSUserDefaults *user = [NSUserDefaults standardUserDefaults];
    [user setObject:data forKey:@"oneStudent"];
//同步到本地
    [user synchronize];

方法2== HXBSaveTool分装类

 [HXBSaveTool  setObject:data forKey:@"oneStudent"];

二、取出对象

1、取出本地保存的data

利用NSUserDefaults或者封装的HXBSaveTool类(//www.greatytc.com/p/ac273e44bd7c 代码解释)
方法1== NSUserDefaults

  NSUserDefaults *user = [NSUserDefaults standardUserDefaults];
   NSData *data = [user objectForKey:@"oneStudent"];

方法2== HXBSaveTool分装类

 NSData *data = [HXBSaveTool  objecForKey:@"oneStudent"];

2、将data解档为对象

Student *student = [NSKeyedUnarchiver unarchiveObjectWithData:data];

三、保存数组自定义对象

如果要保存对象数组到到本地
对象实现NSCoding协议，代码如下：
存数组对象

//存储信息
            NSData *data = [HXBSaveTool valueForKey:kRecorde];
            NSMutableArray *dataArr;
            if (data) {
                dataArr = [NSKeyedUnarchiver unarchiveObjectWithData:data];
            }else{
                dataArr = [NSMutableArray array];
            }
            OpenRecordeModel *recorde = [OpenRecordeModel new];
            recorde.pid = model.pid;
            recorde.tel = [HXBSaveTool valueForKey:kUserPhone];
            recorde.crjldate = [formatter stringFromDate:[NSDate date]];
            [dataArr addObject:recorde];
            [HXBSaveTool setValue:[NSKeyedArchiver archivedDataWithRootObject:dataArr] forKey:kRecorde];

取数组对象

_dataArr = [NSKeyedUnarchiver unarchiveObjectWithData:[HXBSaveTool valueForKey:kRecorde]];