iOS常用的数据持久化方案主要有四种：NSUserDefault、File、Keychain、FMDB。

NSUserDefaults

model

student.h

#import <Foundation/Foundation.h>

@interface student : NSObject <NSCoding>

@property (nonatomic, strong) NSNumber *number;
@property (nonatomic, strong) NSString *sex;
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSNumber *age;


@end

student.m

#import "student.h"

@implementation student


- (instancetype)init
{
    self = [super init];
    if (self) {
//        _number = @(1);
        _name = @"zhiajf";
        _age = @(2763);
        _sex = @"男";
    }
    return self;
}



/* 
 编码器
 Encodes the receiver using a given archiver(归档器).
 */
- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:self.number forKey:@"number"];
    [aCoder encodeObject:self.name forKey:@"name"];
    [aCoder encodeObject:self.age forKey:@"age"];
    [aCoder encodeObject:self.sex forKey:@"sex"];
}


/*
 译码器
 Returns an object initialized from data in a given unarchiver（取档器）.
 You typically return self from initWithCoder:. If you have an advanced need that requires substituting a different object after decoding, you can do so in awakeAfterUsingCoder:.
 */
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder
{
    self.number = [aDecoder decodeObjectForKey:@"number"];
    self.name = [aDecoder decodeObjectForKey:@"name"];
    self.age = [aDecoder decodeObjectForKey:@"age"];
    self.sex = [aDecoder decodeObjectForKey:@"sex"];
    return self;
}

@end

    NSLog(@"****%@****",[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]);

    
    student *aStudent = [[student alloc] init];
    aStudent.number = @1;
    
    student *aStudent2 = [[student alloc] init];
    aStudent2.number = @2;
    aStudent2.name = @"第二个stu";
    
    /*********************** NSUserDefault **********************/
    
    NSData *data = [NSKeyedArchiver archivedDataWithRootObject:aStudent];
   
    [[NSUserDefaults standardUserDefaults] setObject:data forKey:@"student"];
    NSData *studentData = [[NSUserDefaults standardUserDefaults] objectForKey:@"student"];
    
    student *studentModel = [NSKeyedUnarchiver unarchiveObjectWithData:studentData];
    
    NSLog(@"****%@****",studentModel.sex);

File

/*********************** file **********************/
    
    NSString *path =  [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    path = [path stringByAppendingString:@"/my.archive"];
    
    NSArray *array = @[aStudent,aStudent2];
    
    [NSKeyedArchiver archiveRootObject:array toFile:path];
    NSArray *array2 = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    /*
     [NSKeyedArchiver archiveRootObject:aStudent toFile:path];
     student *stuArchiver = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
 
     [NSKeyedArchiver archiveRootObject:aStudent2 toFile:path];
     student *stuArchiver2 = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
     */
    student *stuArchiver = array2[0];
    student *stuArchiver2 = array2[1];
    
//    NSLog(@"****%@****",stuArchiver.name);
//    NSLog(@"****%@****",stuArchiver2.name);

Keychain

/*********************** keychain **********************/
    /*
     参考
     http://www.jianshu.com/p/9188235eedab
     https://github.com/v2panda/PDKeyChain
     */

FMDB

    // 创建db
    NSString *path =  [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSLog(@"****%@****",path);
    
    
    path = [path stringByAppendingString:@"/User.db"];
    
    //实例化一个FMDatabase对象，并打开一个数据库，如果没有这个数据库，就会创建一个数据库
    FMDatabase *db = [FMDatabase databaseWithPath:path];
    
    // 打开db
    [db open];
    if(![db open]) {
        return;
    }
    // 增删改查
    /*
     create\update\insert\alter\begin\detach
     
     */
    
    
    
    //创建表
    [db executeUpdate:@"CREATE TABLE Users(Name text,Age integer)"];
    
    
    //插入数据
    [db executeUpdate:@"INSERT INTO Users(Name,Age)VALUES(?,?)",@"Eric",[NSNumber numberWithInt:25]];
    
    
    NSString *userName1 = [db stringForQuery:@"SELECT Name FROM Users WHERE Age = ?",@"25"];
    
    NSLog(@"%@", userName1);
    
   
    
    // 更新数据
    [db executeUpdate:@"UPDATE Users SET Name = ? WHERE Name = ?",@"Michael",@"Eric"];
    NSLog(@"%@", userName1);
    
    
    
    //删除数据
    [db executeUpdate:@"DELETE FROM Users WHERE Name = ?",@"Michael"];
    
    
    
    //查询数据
    NSString *userName = [db stringForQuery:@"SELECT Name FROM Users WHERE Age = ?",@"25"];
    NSLog(@"%@", userName);
    
    
    //查询多个数据,FMResultSet类，是一个结果集，返回多条数据，FMDB会将数据放在这个结果集中，然后在对这个结果集进行查询即可
    FMResultSet *res = [db executeQuery:@"SELECT * FROM Users"];
    res = [db executeQuery:@"SELECT * FROM Users WHERE Age = ?",@"25"];
    while ([res next]) {
        NSString *name = [res stringForColumn:@"Name"];
        
        NSString *age = [res stringForColumn:@"Age"];
        NSLog(@"%@%@", name, age);
    }
    
    
    // 关闭db
    [db close];

// 使用FMDatabaseQueue类实现多线程操作
    
    FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:fileName];
    [queue inDatabase:^(FMDatabase *db) {
        
        [db executeUpdate:@"create table if not exists t_student_q (id integer primary key autoincrement, name text not null, age integer not null)"];
        
        int age = 42;
        NSString *name = @"name 1";
        
        //1.executeUpdate:不确定的参数用？来占位（后面参数必须是oc对象，；代表语句结束）
        [db executeUpdate:@"INSERT INTO t_student_q (name, age) VALUES (?,?);",name,@(age)];
        
        FMResultSet *rs = [db executeQuery:@"select * from t_student_q"];
        
        while([rs next]) {
            NSString *name = [rs objectForColumnName:@"name"];

            NSLog(@"****%@==****",name);
        }
    }];

参考
FMDB
FMDB多线程安全问题