SecondViewController *secondvc = [SecondViewController new];
//創(chuàng)建系統(tǒng)單例 NSUserDefaults的實(shí)例對(duì)象
 NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
//存值
[defaults setObject:_firsttextfield.text forKey:@"firstTGP"];
  NSLog(@"%@",defaults);

  [self.navigationController pushViewController:secondvc animated:YES];

//創(chuàng)建對(duì)象來(lái)獲取存好的數(shù)據(jù)
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
//接收數(shù)據(jù)
NSString *str = [defaults objectForKey:@"firstTGP"];
//賦值到控件
_secondlabel.text = str;

#pragma mark---第一種方法:
//創(chuàng)建單例方法使用加號(hào)的原因:在創(chuàng)建之前無(wú)法存在一個(gè)實(shí)例對(duì)象去調(diào)用
+(instancetype)sharedDatahandle{
//為了線程安全(添加線程鎖)
  @synchronized(self) {
    if (!dataHandle) {
      dataHandle = [[DataHandle alloc]init];
    }
  }

  return dataHandle;
}

#pragma mark---第二種方法:

+(instancetype)sharedDatahandle{
  static DataHandle *dataHandle = nil;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    dataHandle = [[DataHandle alloc]init];
  });

  return dataHandle;
}

 self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]initWithTitle:@"back" style:UIBarButtonItemStylePlain target:self action:@selector(backAC)];
  DataHandle *handle = [DataHandle sharedDatahandle];
  handle.title = @"年薪";
- (void)backAC{
  [self.navigationController popViewControllerAnimated:YES];

}

- (void)viewWillAppear:(BOOL)animated{//從后往前傳時(shí)的取值操作
  //取值(同樣不能寫(xiě)在ViewDidLoad中)
  DataHandle *handle = [DataHandle sharedDatahandle];
  self.firstLabel.text = handle.title;
}

  //使用NSUserDefault進(jìn)行存儲(chǔ)
  //1:創(chuàng)建要存儲(chǔ)的數(shù)組
  NSArray *array = @[@"11", @"22",@"33"];
  //創(chuàng)建NSUserDefault對(duì)象
  NSUserDefaults *user = [NSUserDefaults standardUserDefaults];
  [user setObject:array forKey:@"userArray"];
  NSLog(@"%@",user);

  //讀取
  NSArray *newarr = [user objectForKey:@"userArray"];
  NSLog(@"%@",newarr);

#warning 注意：對(duì)相同的Key賦值約等于一次覆蓋，要保證每一個(gè)Key的唯一性
// NSUserDefaults 存儲(chǔ)的對(duì)象全是不可變的（這一點(diǎn)非常關(guān)鍵，弄錯(cuò)的話程序會(huì)出bug），例如，如果我想要存儲(chǔ)一個(gè) NSMutableArray 對(duì)象，我必須先創(chuàng)建一個(gè)不可變數(shù)組（NSArray）再將它存入NSUserDefaults中去
NSMutableArray *mutableArray = [NSMutableArray arrayWithObjects:@"123",@"234",@"456", nil];
NSArray *array1 = [NSArray arrayWithArray:mutableArray];
NSUserDefaults *user2 = [NSUserDefaults standardUserDefaults];
[user2 setObject:array1 forKey:@"我們這里存放的一定是不可變的"];

//  取出數(shù)據(jù)是一樣的，想要用NSUserDefaults中的數(shù)據(jù)給可變數(shù)組賦值
/*-------------- 錯(cuò)誤方法 --------------*/
//    NSMutableArray *mutablearray = [user objectForKey:@"我們這里存放的一定是不可變的"];
//  //這樣寫(xiě)后，mutableArray 就變成了不可變數(shù)組了，如果你要在數(shù)組中添加或刪除數(shù)據(jù)就會(huì)出現(xiàn)bug
//  NSLog(@"%@",mutablearray);

/*------  正確 --------*/
NSMutableArray *mutablearray = [NSMutableArray arrayWithArray:[user2 objectForKey:@"我們這里存放的一定是不可變的"]];
NSLog(@"%@",mutablearray);