使浮点只显示两位小数

Question

我有值25.00的float,但是当我打印在屏幕上它25.0000000.
如何只用两位小数显示值？

Answer 1

这不是数字如何存储的问题,而是您如何显示它的问题.将其转换为字符串时,必须舍入到所需的精度,在您的情况下是两位小数.

例如:

NSString* formattedNumber = [NSString stringWithFormat:@"%.02f", myFloat];

%.02f告诉格式化程序你将格式化一个float(%f),并且应该舍入到两个地方,并且应该用0s 填充.

例如:

%f = 25.000000
%.f = 25
%.02f = 25.00

Answer 2

以下是一些更正 -

//for 3145.559706

斯威夫特3

let num: CGFloat = 3145.559706
print(String(format: "%f", num)) = 3145.559706
print(String(format: "%.f", num)) = 3145
print(String(format: "%.1f", num)) = 3145.6
print(String(format: "%.2f", num)) = 3145.56
print(String(format: "%.02f", num)) = 3145.56 // which is equal to @"%.2f"
print(String(format: "%.3f", num)) = 3145.560
print(String(format: "%.03f", num)) = 3145.560 // which is equal to @"%.3f"

OBJ-C

@"%f"    = 3145.559706
@"%.f"   = 3146
@"%.1f"  = 3145.6
@"%.2f"  = 3145.56
@"%.02f" = 3145.56 // which is equal to @"%.2f"
@"%.3f"  = 3145.560
@"%.03f" = 3145.560 // which is equal to @"%.3f"

等等...

Answer 3

您也可以尝试使用NSNumberFormatter:

NSNumberFormatter* nf = [[[NSNumberFormatter alloc] init] autorelease];
nf.positiveFormat = @"0.##";
NSString* s = [nf stringFromNumber: [NSNumber numberWithFloat: myFloat]];

你可能还需要设置负面格式,但我认为它很聪明,可以搞清楚.

Answer 4

我根据上述答案迅速进行了扩展

extension Float {
    func round(decimalPlace:Int)->Float{
        let format = NSString(format: "%%.%if", decimalPlace)
        let string = NSString(format: format, self)
        return Float(atof(string.UTF8String))
    }
}

用法:

let floatOne:Float = 3.1415926
let floatTwo:Float = 3.1425934
print(floatOne.round(2) == floatTwo.round(2))
// should be true

Answer 5

在Swift语言中,如果你想表明你需要以这种方式使用它.要在UITextView中指定double值,例如:

let result = 23.954893
resultTextView.text = NSString(format:"%.2f", result)

如果你想在LOG中显示像objective-c那样使用NSLog(),那么在Swift语言中你可以这样做:

println(NSString(format:"%.2f", result))