Question

我有一个漂浮的距离，我正在寻找一种方法来为人类读者很好地格式化它。理想情况下，我希望它随着它变大而从m变为km，并且很好地将数字四舍五入。转换为里程将是一个奖励。我相信很多人都需要其中一个，我希望有一些代码可以在某个地方浮动。

以下是我喜欢的格式：

0-100m：47m（整数）
100-1000m：325m或320m（圆到最近的5或10米）
1000-10000m：1.2km（圆形到最近，小数点后一位）
10000m +：21km

如果没有可用的代码，我该如何编写自己的格式化程序？

由于

Answer 1

这些解决方案都没有真正符合我的要求，所以我建立了它们：

#define METERS_TO_FEET  3.2808399
#define METERS_TO_MILES 0.000621371192
#define METERS_CUTOFF   1000
#define FEET_CUTOFF     3281
#define FEET_IN_MILES   5280

- (NSString *)stringWithDistance:(double)distance {
    BOOL isMetric = [[[NSLocale currentLocale] objectForKey:NSLocaleUsesMetricSystem] boolValue];

    NSString *format;

    if (isMetric) {
        if (distance < METERS_CUTOFF) {
            format = @"%@ metres";
        } else {
            format = @"%@ km";
            distance = distance / 1000;
        }
    } else { // assume Imperial / U.S.
        distance = distance * METERS_TO_FEET;
        if (distance < FEET_CUTOFF) {
            format = @"%@ feet";
        } else {
            format = @"%@ miles";
            distance = distance / FEET_IN_MILES;
        }
    }

    return [NSString stringWithFormat:format, [self stringWithDouble:distance]];
}

// Return a string of the number to one decimal place and with commas & periods based on the locale.
- (NSString *)stringWithDouble:(double)value {
    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
    [numberFormatter setLocale:[NSLocale currentLocale]];
    [numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
    [numberFormatter setMaximumFractionDigits:1];
    return [numberFormatter stringFromNumber:[NSNumber numberWithDouble:value]];
}

- (void)viewDidLoad {
    [super viewDidLoad];

    double distance = 5434.45;
    NSLog(@"%f meters is %@", distance, [self stringWithDistance:distance]);

    distance = 543.45;
    NSLog(@"%f meters is %@", distance, [self stringWithDistance:distance]);    

    distance = 234234.45;
    NSLog(@"%f meters is %@", distance, [self stringWithDistance:distance]);    
}

Answer 2

iOS 7和OS X 10.9引入了MKDistanceFormatter来格式化距离：

代码示例：

double myDistance = 21837.0f;

MKDistanceFormatter *df = [[MKDistanceFormatter alloc]init];
df.unitStyle = MKDistanceFormatterUnitStyleAbbreviated;

NSLog(@"myDistance is %@", [df stringFromDistance: myDistance]);

<强>更新

似乎MKDistanceFormatter以某种方式舍入输入值。例如。当我将myDistance设置为111.0时，我得到“100米”。

Answer 3

是的，您需要编写自己的格式化程序，例如

#include <math.h>
NSString* convertDistanceToString(float distance) {
    if (distance < 100)
       return [NSString stringWithFormat:@"%g m", roundf(distance)];
    else if (distance < 1000)
       return [NSString stringWithFormat:@"%g m", roundf(distance/5)*5];
    else if (distance < 10000)
       return [NSString stringWithFormat:@"%g km", roundf(distance/100)/10];
    else
       return [NSString stringWithFormat:@"%g km", roundf(distance/1000)];
}
...
NSLog(@"The distance is %@", convertDistanceToString(1024));

Answer 4

iOS 8和OS X 10.10中引入的

NSLengthFormatter是人们应该注意的选项。

    NSLengthFormatter *lengthFormatter = [[NSLengthFormatter alloc] init];
    lengthFormatter.unitStyle = NSFormattingUnitStyleShort;

    NSLog(@"distance = %@", [lengthFormatter stringFromMeters:meters]);

但是，NSLengthFormatter在使用指标的区域设置中不使用英制单位，除了距离。

Answer 5

我是这样做的。这使用用户的语言环境来正确格式化字符串，您也应该这样做。

// Returns a string representing the distance in the correct units.
// If distance is greater than convert max in feet or meters, 
// the distance in miles or km is returned instead
NSString* getDistString(float distance, int convertMax, BOOL includeUnit) {
  NSString * unitName;
  if (METRIC) {
    unitName = @"m";
    if (convertMax != -1 && distance > convertMax) {
      unitName = @"km";
      distance = distance / 1000;
    }
  } else {
    unitName = @"ft";
    if (convertMax != -1 && distance > convertMax) {
      unitName = @"mi";
      distance = distance / 5280;
    }
    distance = metersToFeet(distance);
  }

  if (includeUnit) return [NSString stringWithFormat:@"%@ %@", formatDecimal_1(distance), unitName];

  return formatDecimal_1(distance);

}
// returns a string if the number with one decimal place of precision
// sets the style (commas or periods) based on the locale
NSString * formatDecimal_1(float num) {
  static NSNumberFormatter *numFormatter;
  if (!numFormatter) {
    numFormatter = [[[NSNumberFormatter alloc] init] retain];
    [numFormatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
    [numFormatter setLocale:[NSLocale currentLocale]];
    [numFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
    [numFormatter setMaximumFractionDigits:1];
    [numFormatter setMinimumFractionDigits:1];
  }

  return [numFormatter stringFromNumber:F(num)];

}

Answer 6

今天发现这个问同样的问题....跟着：

 NSString *rvalue;
    if (value > 1000) {
        rvalue = [NSString stringWithFormat:@"%.02f km",value];
    }else {
        rvalue = [NSString stringWithFormat:@"%.02f m",value];
    }

如果需要，

可以将其包装在一个方法中

Answer 7

对于那些寻找swift 2.0版本的人。来自@MattDiPasquale

 extension Double {
  func toDistanceString() -> String {
    let METERS_TO_FEET = 3.2808399
    let METERS_CUTOFF = 1000.0
    let FEET_CUTOFF = 3281.0
    let FEET_IN_MILES =  5280.0

    let format:String
    if (NSLocale.isMetric()) {
      if (self < METERS_CUTOFF) {
        format = "\(self.stringWithDecimals(0)) metres"
      } else {
        format = "\((self / 1000).stringWithDecimals(1)) km";
      }
    } else { // assume Imperial / U.S.
      let feet = self * METERS_TO_FEET;
      if (feet < FEET_CUTOFF) {
        format = "\(feet.stringWithDecimals(0)) feet";
      } else {
        format = "\((self / FEET_IN_MILES).stringWithDecimals(1)) miles";
      }
    }
    return format
  }

  func stringWithDecimals(decimals:Int) -> String {
    return String(format: "%.\(decimals)f", self)
  }
}

extension NSLocale {
  class func isMetric() -> Bool {
    let locale = NSLocale.currentLocale()
    return locale.objectForKey(NSLocaleUsesMetricSystem) as! Bool
  }
}

目标c字符串格式化距离

7 个答案: