无意冒犯但你的代码就是一堆垃圾
1.名为something的变量没有用。句号。
1.你的局部方法中有一个名为something的变量。你有一个名为something的变量，它是你的类的一部分。“局部变量隐藏示例变量”警告是有原因的！
也许这就是你所有问题的来源。我认为你并没有真正理解局部变量的概念。如果是这样的话，你应该阅读更多关于Objective-C的基本内容。
1.你检查是否有值为nil，然后你不改变什么，只分配一个数组。这两个人没有任何关系。不要写这样的代码。
我帮你修好了：

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSArray *anArr = [userDefaults objectForKey:@"somedata"];
    NSLog(@"anArr::: %@",anArr);
}

-(IBAction)addsomething:(id)sender{
    NSMutableArray *array = [[NSMutableArray alloc] init];
    NSLog(@"textfieldvalue::: %@", textfield.text);
    [array addObject:textfield.text];
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults setObject:array forKey:@"somedata"];
    array = [userDefaults objectForKey:@"somedata"];

    // synchronize is only needed while debugging (when you use the stop button in Xcode)
    // you don't need this in production code. remove it for release
    [userDefaults synchronize];

    NSLog(@"array:: %@", array);
}

但是，您很可能希望将对象保存到从userDefaults获得的数组中。这对局部变量不起作用！
你会用这样的东西。但别一字不差地抄。试着理解它，并阅读更多关于局部变量的内容。

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
array = [[userDefaults objectForKey:@"somedata"] mutableCopy];
if (!array) {
    // create array if it doesn't exist in NSUserDefaults
    array = [[NSMutableArray alloc] init];
}
NSLog(@"array in viewDidLoad: %@",array);


NSLog(@"textfieldvalue::: %@", textField.text);
[array addObject: textField.text];
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
[userDefaults setObject:array forKey:@"somedata"];

// synchronize is only needed while debugging (when you use the stop button in Xcode)
// you don't need this in production code. remove it for release
[userDefaults synchronize];

请尝试以下代码：

- (void)viewDidLoad
{
 [super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

NSUserDefaults *somet = [NSUserDefaults standardUserDefaults];

NSMutableArray *anArr = [[NSMutableArray alloc] init];
 anArr = [somet objectForKey:@"somedata"] ;
[somet synchronize];

NSLog(@"anArr::: %@",anArr);

}

-(IBAction)addsomething:(id)sender{

NSLog(@"textfieldvalue::: %@", textfield.text);
//Here u have to check array is in memory allocate or not 
[array addObject:textfield.text];

NSUserDefaults *something = [NSUserDefaults standardUserDefaults];

[something setObject:array forKey:@"somedata"];
[something synchronize];

array = [something objectForKey:@"somedata"];

NSLog(@"array:: %@", array);

}

您需要在setObject:forKey之后调用[[NSUserDefaults standardUserDefaults] synchronize];。

[something setObject:array forKey:@"somedata"];
[something synchronize];

添加这一行，

[something synchronize]

在检索数据之前。

在将值保存到NSUserDefaults中时尝试此操作

- (void)savingObject:(NSString *)keyName data:(id)val
{
    NSData *dataVal = [NSKeyedArchiver archivedDataWithRootObject:val];
    [defaults setObject:dataVal forKey:keyName];
    [defaults synchronize];
}

然后当你想要的时候用这个

- (id)gettingObject:(NSString *)keyName
{
    NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:keyName];
    return [NSKeyedUnarchiver unarchiveObjectWithData:data];
}

我想这对你有帮助