ios - NSUserDefault 字符串无法检索并转换为 double

Question

我正在为 NSUserDefault 保存一个值。

原值是double，我把它转成NSNumber，然后存为字符串。 我在保存时打印了这些值，并且它们设置正确。

检索时，我获取字符串值并将其转换为 double 值。但是 string 和 double 值都没有给出任何东西。 string 给出 null，double 给出 0.000

保存

//convert filtersequcne to NSNumber...finally saved as string

            NSNumber *myDoubleNumber = [NSNumber numberWithDouble:filtersequence];
            NSLog(@"Value being stored in myDoubleNumber %@",myDoubleNumber);


            // save string with input name of filter for that key
            NSUserDefaults *combination = [NSUserDefaults standardUserDefaults];
            [combination setObject:[myDoubleNumber stringValue] forKey:input];

            NSLog(@"Value of [mydoublenumber] string value %@",[myDoubleNumber stringValue]);

取回值

//get input from saved filter
    NSUserDefaults *fetchcombination = [NSUserDefaults standardUserDefaults];

    // get the string
    NSString *message = [fetchcombination objectForKey:@"Test"];
    NSLog(@"Value of message %@",message);

    // convert string to double
    double actualdoublecombination = [message doubleValue];
    NSLog(@"Value of double actualdoublecombination %f",actualdoublecombination);

Answer 1

这是您保存/读取 double 的方式:

double value = 42.00;
[[NSUserDefaults standardUserDefaults] setDouble:value forKey:@"MyDouble"];

double value = [[NSUserDefaults standardUserDefaults] doubleForKey:@"MyDouble"];