objective-c - NSNumber:stringValue 崩溃，描述有效

Question

[measureValue stringValue] 给了我这个异常:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFString stringValue]: unrecognized selector sent to instance 0x4dde570'

[measureValue 描述] 完美运行

但我认为我应该在代码中使用stringValue，对吗？

这是代码:

NSNumber *measureValue = [NSString stringWithFormat:@"%i", [cellContent integerValue]];

//if imperial (inches)
if ([[[NSUserDefaults standardUserDefaults] stringForKey:@"Measure"] isEqualToString:@"Imperial"] ) {

    //if height
    if ([currentQuestion isEqualToString:@"Height"]) {
        measureValue = [NSNumber numberWithDouble:(2.54 * [measureValue doubleValue])];
    //elseif weight
    } else {
        measureValue = [NSNumber numberWithDouble:(0.45359237 * [measureValue doubleValue])];
    }

    //NSLog(@"%@", [measureValue stringValue]);
    cellContent = [measureValue description];

Answer 1

 NSNumber *measureValue = [NSString stringWithFormat:@"%i", [cellContent integerValue]];

该行返回一个 NSString，而不是 NSNumber。您正在将 stringValue 发送到 NSString。