迅速向下舍入

Question

我想将Double加倍到一定数量的小数,总是四舍五入.

例

舍入到.00 => 1.5679999到1.56

舍入到.000 => 1.5679999到1.567

round(1.5679999 * 100) / 100 //returns 1.57
round(1.5679999 * 1000) / 1000 //returns 1.568

我想要一个Double而不是一个连接的字符串

Answer 1

只需更换round用floor!

Answer 2

截至swift 3.0:

myDouble.rounded(.down)

Answer 3

SWIFT4+

处理不同情况的方法

var w = 6.5
w.round(.toNearestOrAwayFromZero)
// w == 7.0

// Equivalent to the C 'trunc' function:
var x = 6.5
x.round(.towardZero)
// x == 6.0

// Equivalent to the C 'ceil' function:
var y = 6.5
y.round(.up)
// y == 7.0

// Equivalent to the C 'floor' function:
var z = 6.5
z.round(.down)
// z == 6.0