- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:name forKey:@"MY_NAME"];
    [aCoder encodeInt32:age forKey:@"MY_AGE"];

}

-(id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];
    if(self)
    {
        name = [aDecoder decodeObjectForKey:@"MY_NAME"];
        age = [aDecoder decodeIntForKey:@"MY_AGE"];

    }
    return self;
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    NSString *path = [self filePath:@"test.txt"];
    if ([[NSFileManager defaultManager] fileExistsAtPath:path])
    {
        NSData *data = [[NSMutableData alloc] initWithContentsOfFile:path];
        NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        MyObject *obj = [unarchiver decodeObjectForKey:@"MY_OBJ"];
        [unarchiver finishDecoding];
    NSLog(@"name %@ age %d color %@", obj.name, obj.age,
              obj.color);
    }
    return YES;
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    NSString *path = [self filePath:@"test.txt"];
    if ([[NSFileManager defaultManager] fileExistsAtPath:path])
    {
        NSLog(@"file exist");
    }
    else
    {
        NSLog(@"create file");
        MyObject *myObj = [[MyObject alloc] init];
        myObj.name = @"peter";
        myObj.age = 18;
        myObj.color = @"blue";
    NSMutableData *data = [[NSMutableData alloc] init];
        NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
        [archiver encodeObject:myObj forKey:@"MY_OBJ"];
        [archiver finishEncoding];
        [data writeToFile:path atomically:YES];
    }
}