Question

NSNumberFormatter正在返回垃圾数据。感兴趣的变量底部是 milesString 。它是四舍五入而不是1.6388。我输入了调试器信息，还添加了testString和num2的调试代码。作为参考，DistanceFormatter是静态的，除了这个函数以外的任何地方都没有修改。我已经尝试用本地实例替换它以查看静态对象是否导致了问题（事实并非如此）。另一个注意事项，当我没有使用roudingMode时，我收到了这个错误。

-(NSString *)distanceStringFromLocation:(CLLocation *)location {
    if (!DistanceFormatter) {
        DistanceFormatter = [NSNumberFormatter alloc];
        [DistanceFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
        DistanceFormatter.roundingMode = NSNumberFormatterRoundCeiling;
        DistanceFormatter.minimumFractionDigits = 0;
        DistanceFormatter.maximumFractionDigits = 4;
    }
    CLLocationDistance distance = [_location distanceFromLocation:location];
    distance = distance / 1000;
    NSLocale *locale = [NSLocale currentLocale];
    BOOL isMetric = [[locale objectForKey:NSLocaleUsesMetricSystem] boolValue];
    if (isMetric) {

        return [NSString stringWithFormat:@"%@ kilometers away", [DistanceFormatter stringFromNumber:[NSNumber numberWithFloat:distance]]];
    } else {
        CGFloat miles = 0.621371 * distance; //miles = (CGFloat) 1.63877738
        NSNumber *num = [NSNumber numberWithFloat:miles]; //num = (__NSCFNumber *)(float)1.63878
        NSString *testString = [NSString stringWithFormat:@"%f", miles]; //testString = (__NSCFString *) @"1.63877"
        NSNumber *num2 = [DistanceFormatter numberFromString:testString]; //num2 = (NSNumber *)nil
        NSString *milesString = [DistanceFormatter stringFromNumber:num]; //milesString = (__NSCFString *)@"2"
        return [NSString stringWithFormat:@"%@ miles away", milesString];
    }
}

Answer 1

您已分配但未初始化日期格式化程序。

DistanceFormatter = [NSNumberFormatter alloc];

应该是

DistanceFormatter = [[NSNumberFormatter alloc] init];

通过该更改，您可以获得结果milesString = @"1.6388"。

ios7 NSNumberFormatter十进制样式意外输出

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