目标C中的舍入数

感谢各位的指点,我已经想出了一个解决方案:

float roundedValue = round(2.0f * number) / 2.0f;
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setMaximumFractionDigits:1];
[formatter setRoundingMode: NSNumberFormatterRoundDown];

NSString *numberString = [formatter stringFromNumber:[NSNumber numberWithFloat:roundedValue]];
[formatter release];

上面的内容适用于我抛出的测试用例,但是如果有人知道更好的方法来做这件事,我会感兴趣的听到它!

float floatVal = 1.23456;

舍入

int roundedVal = lroundf(floatVal); 

NSLog(@"%d",roundedVal);

舍入

int roundedUpVal = ceil(floatVal); 

NSLog(@"%d",roundedUpVal);

舍入

int roundedDownVal = floor(floatVal);

NSLog(@"%d",roundedDownVal);

NSString *numberString = [NSString stringWithFormat:@"%f", round(2.0f * number) / 2.0f];

使用lRoundf()将浮点数舍入为整数,然后将整数转换为字符串。

NSString *numberString = [NSString stringWithFormat:@"%d",lroundf(number)];

我建议你研究一下 NSNumberFormatter .

一个简单的方法:

float theFloat = 1.23456;
int rounded = roundf(theFloat); NSLog(@"%d",rounded);
int roundedUp = ceil(theFloat); NSLog(@"%d",roundedUp);
int roundedDown = floor(theFloat); NSLog(@"%d",roundedDown);
// Note: int can be replaced by float

NSString *intNumberString = [NSString stringWithFormat:@"%d", (int)floatNumber];

以下技术在财务应用程序中对我很有用。

 NSString *dd=[NSString stringWithFormat:@"%0.2f",monthlyPaymentCalculated];

        monthlyPaymentCalculated=[dd doubleValue];

self.monthlyPaymentCritical=monthlyPaymentCalculated;

首先用%0.2f将它四舍五入并存储在nsstring中,然后我将它再次转换为double,结果对我的计算很好。

通过这些函数,您可以四舍五入到任何值。如果使用p=2,则得到偶数。

float RoundTo(float x, float p)
{
  float y = 1/p;
  return int((x+(1/(y+y)))*y)/y;
}

float RoundUp(float x, float p)
{
  float y = 1/p;
  return int((x+(1/y))*y)/y;
}

float RoundDown(float x, float p)
{
  float y = 1/p;
  return int(x*y)/y;
}

我需要能够四舍五入到一个特定的数字(不一定是整数)。我做了一个 NSNumber 类别(基于 Ash's answer )并添加了以下方法:

- (NSString *)stringByRounding:(NSNumberFormatterRoundingMode)roundingMode
      toPositionRightOfDecimal:(NSUInteger)position
{
    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    [formatter setMaximumFractionDigits:position];
    [formatter setRoundingMode:roundingMode];
    NSString *numberString = [formatter stringFromNumber:self];
    return numberString;
}

它允许我这样使用它:

[aNumber stringByRounding:NSNumberFormatterRoundUp toPositionRightOfDecimal:2];

我可以用它通过传入整数 0 作为第二个参数:

[aNumber stringByRounding:NSNumberFormatterRoundPlain toPositionRightOfDecimal:0];