在swift中将双精度值四舍五入到x个小数位数 [英] Rounding a double value to x number of decimal places in swift

问题描述

谁能告诉我如何在 Swift 中将 double 值四舍五入到 x 位小数?

Can anyone tell me how to round a double value to x number of decimal places in Swift?

我有:

var totalWorkTimeInHours = (totalWorkTime/60/60)

totalWorkTime 是秒内的 NSTimeInterval(双精度).

With totalWorkTime being an NSTimeInterval (double) in second.

totalWorkTimeInHours 会给我小时数，但它给了我这么长的精确数字的时间量，例如1.543240952039......

totalWorkTimeInHours will give me the hours, but it gives me the amount of time in such a long precise number e.g. 1.543240952039......

当我打印 totalWorkTimeInHours 时，如何将其舍入到 1.543?

How do I round this down to, say, 1.543 when I print totalWorkTimeInHours?

推荐答案

你可以使用 Swift 的 round 函数来完成这个.

You can use Swift's round function to accomplish this.

要将 Double 以 3 位精度舍入，首先将其乘以 1000，然后将其舍入并将舍入后的结果除以 1000:

To round a Double with 3 digits precision, first multiply it by 1000, round it and divide the rounded result by 1000:

let x = 1.23556789
let y = Double(round(1000 * x) / 1000)
print(y) /// 1.236

与任何一种printf(...) 或 String(format: ...) 解决方案不同，此操​​作的结果仍然是 类型双重.

Unlike any kind of printf(...) or String(format: ...) solutions, the result of this operation is still of type Double.

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