ios - NSMutableDictionary 和 NSUserDefaults

Question

我正在尝试找出正确的数据结构来保存 'date' => 'value' 的键值

我正在尝试使用 NSMutableDictionary，因为每次用户输入值并按下“保存”时它都必须保存。

但是，尝试将 NSLog 字典的值始终为 null。

- (IBAction)saveWeight:(id)sender
{
    NSMutableDictionary *weightLog = [[NSMutableDictionary alloc] init];
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];

    NSString *date = @"12/12/14"; 

    [weightLog setObject:self.weightInput.text forKey:date];

    NSLog(@"neweight you entered is %@", self.weightInput.text);
    NSLog(@"weightlog is %@", weightLog);

    [userDefaults setObject:weightLog forKey:@"Weightlog"];
    [userDefaults synchronize];
}

日志输出:

diet[35744:70b] neweight you entered is 13
2014-03-01 16:25:58.712 diet[35744:70b] weightlog is {
"12/12" = 13;
}

Answer 1

当然，只有最后一个值被保存，因为在添加新值之前您不会在 weightLog 中加载以前的值!还有一件事，您应该更改每个值的键。

尝试使用这个(日期将包括年+月+日+时+分+秒，所以每秒点击次数不要超过1次；-D):

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];

NSMutableDictionary *weightLog = [NSMutableDictionary dictionaryWithDictionary:[userDefaults objectForKey:@"Weightlog"]];


NSString *date = [NSDateFormatter localizedStringFromDate:[NSDate date]
                                                dateStyle:NSDateFormatterShortStyle
                                                timeStyle:NSDateFormatterFullStyle];

[weightLog setObject:self.weightInput.text forKey:date];

NSLog(@"neweight you entered is %@", self.weightInput.text);
NSLog(@"weightlog is %@", weightLog);

[userDefaults setObject:weightLog forKey:@"Weightlog"];
[userDefaults synchronize];