从float获取字符串而不舍入其值 [英] Get string from float without rounding its value

问题描述

我正面临一种情况，在这种情况下，我只需要在float的小数点后保留2位，而无需舍入其实际值.

I am facing one scenario where I need only 2 places after the decimal point of float without rounding its actual value.

我尝试了以下代码行:

extension Float {

func stringWith2Decimals() -> String {
    return String(format: "%.2f", self)
  }
}

这给了我以下输出:

var floatValue = 10.99999999 

输出:11.00

Output: 11.00

预期结果:10.99

Expected result: 10.99

请让我知道您的想法.

推荐答案

经过测试，这将为您提供帮助.

This will help you, I have tested it.

let floatValue = 10.99999999
let formatter = NumberFormatter()
formatter.maximumFractionDigits = 2
formatter.roundingMode = .down
let s = formatter.string(from: NSNumber(value: floatValue))
print(s)

更新的答案为 还有一个案例，其值为10.9，应显示10.90.

Updated answer for one more case is there for value 10.9 it should show 10.90.

情况1:当您只想打印实际的十进制数字或最多2个十进制数字

Case 1: When you only want to print actual decimal digits or max 2 decimal digit

 let floatValue = 10.999999
    let floatValue1 = 10
    let floatValue2 = 10.9
    let floatValue3 = 10.91


    let formatter = NumberFormatter()
    formatter.minimumFractionDigits = 0
    formatter.maximumFractionDigits = 2
    formatter.roundingMode = .down
    let s = formatter.string(from: NSNumber(value: floatValue))
    print(s!)  // 10.99
    let s1 = formatter.string(from: NSNumber(value: floatValue1))
    print(s1!)  // 10
    let s2 = formatter.string(from: NSNumber(value: floatValue2))
    print(s2!)  // 10.9
    let s3 = formatter.string(from: NSNumber(value: floatValue3))
    print(s3!)  // 10.91

情况2:当您始终要打印两位十进制数字时.

Case 2: When you always want to print two decimal digits.

 let floatValue = 10.999999
    let floatValue1 = 10
    let floatValue2 = 10.9
    let floatValue3 = 10.91


    let formatter = NumberFormatter()
    formatter.minimumFractionDigits = 2
    formatter.maximumFractionDigits = 2
    formatter.roundingMode = .down
    let s = formatter.string(from: NSNumber(value: floatValue))
    print(s!) // 10.99
    let s1 = formatter.string(from: NSNumber(value: floatValue1))
    print(s1!) // 10.00
    let s2 = formatter.string(from: NSNumber(value: floatValue2))
    print(s2!) // 10.90
    let s3 = formatter.string(from: NSNumber(value: floatValue3))
    print(s3!) // 10.91

希望您得到想要的东西.如果是，那么请投票，否则让我知道您的实际要求.

Hope you get what you want. if yes then please vote up else let me know what is your actual requirement.

问题的更新答案. 对于诸如10.9999999999999999之类的值，其打印为11.00，而不是10.99.

Updated answer for an issue . for value like 10.9999999999999999 its printing 11.00, Not 10.99.

  let floatValue3 = 10.99999999999999
    let (wholePart, fractionalPart) = modf(floatValue3)
    let stringFractionalPart = "\(fractionalPart)"
    let stringWholePart = "\(Int(wholePart))"

    let aryFractionalPart = stringFractionalPart.components(separatedBy: ".")

    var valueToDisplay = stringWholePart

    if aryFractionalPart.count >= 2 {
        let decimalDigits = aryFractionalPart[1]
        let digit2 = decimalDigits.prefix(2)
        valueToDisplay = "\(valueToDisplay).\(digit2)"
    }

    print(valueToDisplay)

希望我现在能满足您的要求.

Hope now I fulfill your requirement.

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