1. 基本概念

NSUserDefaults适合存储轻量级的本地数据，比如要保存一个登陆界面的数据，用户名、密码。

屏幕快照 2016-12-06 下午4.09.23.png

2. 创建方法

在ViewController.m中

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; min-height: 13.0px}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo}p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #3d1d81}p.p4 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #008400}p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px 'Heiti SC Light'; color: #008400}p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #703daa}p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Menlo; color: #d12f1b}span.s1 {font-variant-ligatures: no-common-ligatures}span.s2 {font-variant-ligatures: no-common-ligatures; color: #bb2ca2}span.s3 {font-variant-ligatures: no-common-ligatures; color: #000000}span.s4 {font: 11.0px 'Heiti SC Light'; font-variant-ligatures: no-common-ligatures}span.s5 {font-variant-ligatures: no-common-ligatures; color: #703daa}span.s6 {font-variant-ligatures: no-common-ligatures; color: #3d1d81}span.s7 {font-variant-ligatures: no-common-ligatures; color: #272ad8}span.s8 {font-variant-ligatures: no-common-ligatures; color: #d12f1b}span.s9 {font: 11.0px 'Heiti SC Light'; font-variant-ligatures: no-common-ligatures; color: #d12f1b}span.s10 {font: 11.0px Menlo; font-variant-ligatures: no-common-ligatures; color: #000000}span.s11 {font: 11.0px Menlo; font-variant-ligatures: no-common-ligatures}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    //创建圆角按钮
    UIButton* btn=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btn.frame=CGRectMake(100, 100, 80, 40);
    [btn setTitle:@"写入文件" forState:UIControlStateNormal];
    //添加事件函数
    [btn addTarget:self action:@selector(pressWrite) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
    
    
    
    UIButton* btnRead=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnRead.frame=CGRectMake(100, 200, 80, 40);
    [btnRead setTitle:@"读出文件" forState:UIControlStateNormal];
    [btnRead addTarget:self action:@selector(pressRead) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnRead];
    
    
}

-(void)pressWrite
{
    //定义一个用户默认数据对象
    //不需要alloc创建，用户默认数据对象单例模式
    //standardUserDefaults：获取全局唯一实例对象
    NSUserDefaults* ud=[NSUserDefaults standardUserDefaults];
    
    
    //存储字符串对象
    //P1 要存储的对象id
    //P2 对象的名字key
    [ud setObject:@"Mike" forKey:@"Name"];
    
    
    //存储数据对象
    NSNumber* num=[NSNumber numberWithInt:100];
    [ud setObject:num forKey:@"Num"];
    
    //存储整型数据
    [ud setInteger:123 forKey:@"Int"];
    
    //存储BOOL类型
    [ud setBool:YES forKey:@"Bool"];
    
    //存储浮点
    [ud setFloat:1.55 forKey:@"Float"];
    
    
    //存储数组
    NSArray* array=[NSArray arrayWithObjects:@"11",@"22",@"33",nil];
    [ud setObject:array forKey:@"Array"];
    
}

-(void)pressRead
{
    NSUserDefaults* ud=[NSUserDefaults standardUserDefaults];
    id object = [ud objectForKey:@"Name"];
    NSString* name=(NSString*)object;
    NSLog(@"name = %@",name);
    
    
    object= [ud objectForKey:@"Num"];
    NSNumber* num=(NSNumber*)object;
    NSLog(@"num = %@",num);
    
    
    NSInteger iV= [ud integerForKey:@"Int"];
    NSLog(@"int = %ld",iV);
    
    BOOL bV=[ud boolForKey:@"Bool"];
    NSLog(@"bV=@d",bV);
}

屏幕快照 2016-12-06 下午4.34.41.png

再次运行的时候，可以让程序直接读取而不存储数据，发现以前保存的数据仍然可以读取到界面上。

其实它存储在应用程序内置的一个plist文件里，这个可以根据路径看到。
比如说这个是你的程序沙盒位置
/UsersLibrary/Application Support/iPhoneSimulator/4.1/Applicati*****/29788E40-AF47-45A0-8E92-3AC0F501B7F4/,（这个是应用程序对应在mac上的位置）
这个下面有/Library/Prefereces，里面有个plist文件，存储的就是你的userDefaults想要删掉的话，用removeObjectForKey或者删掉沙盒，也就是你的应用程序然后重新安装。