NSMutableArray和NSUserdefaults问题iPhone

Question

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

    NSUserDefaults *somet = [NSUserDefaults standardUserDefaults]; 

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

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

} 

-(IBAction)addsomething:(id)sender{ 

    if (something == nil) { 
     array = [[NSMutableArray alloc] init]; 
    } 
    NSLog(@"textfieldvalue::: %@", textfield.text); 

    [array addObject:textfield.text]; 

    NSUserDefaults *something = [NSUserDefaults standardUserDefaults]; 

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

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

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

} 

使用上面的代码，我试图在NSMutableArray中动态保存数据，然后将它保存在NSUserDefaults中。但在检索它时，我得到（null）。即使数据没有被保存在数组中。

如何正确保存数据？

EDITED: 

2012-03-15 15:17:18.431 check[2686:40b] anArr::: (null) 
2012-03-15 15:17:30.160 check[2686:40b] textfieldvalue::: a 
2012-03-15 15:17:30.162 check[2686:40b] array::: (null) 

Answer 1

没有违法，但你的代码是一堆废话。

1. 变量名为something没有用。期。
2. 你有一个变量在你的本地方法中名为something。你有一个变量，它是你类的一部分。 “局部变量隐藏实例变量”警告是有原因的！
   也许这就是你所有的问题来自哪里。我认为你不太了解局部变量的概念。如果是这种情况，你应该阅读更多关于基本Objective-C的东西。
3. 你检查是否有零，然后你不改变的东西，但你分配一个数组。这两者没有任何关系。不要写这样的代码。

我固定它给你：

- (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); 
} 

---

然而，很可能要对象保存到你userDefaults得到了数组。这不适用于局部变量！

你会使用这样的东西。但不要复制这些逐字。尝试了解它，并阅读更多关于局部变量。

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]; 

Answer 2

尝试下面的代码可能会帮助ü...

- (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); 

} 

Answer 3

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

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

Answer 4

加入这一行，

[something synchronize] 

检索数据之前。

Answer 5

试试这个当您保存价值为NSUserDefaults

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

，然后当你想要得到的是使用这种

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

我认为这可以帮助你