下面是我以前如何将一个浮点数截断到小数点后两位
NSLog(@" %.02f %.02f %.02f", r, g, b);
我查了文档和电子书，但还没找到答案。谢谢!
当前回答
也用于四舍五入:
extension Float
{
func format(f: String) -> String
{
return NSString(format: "%\(f)f", self)
}
mutating func roundTo(f: String)
{
self = NSString(format: "%\(f)f", self).floatValue
}
}
extension Double
{
func format(f: String) -> String
{
return NSString(format: "%\(f)f", self)
}
mutating func roundTo(f: String)
{
self = NSString(format: "%\(f)f", self).doubleValue
}
}
x = 0.90695652173913
x.roundTo(".2")
println(x) //0.91
其他回答
斯威夫特4
let string = String(format: "%.2f", locale: Locale.current, arguments: 15.123)
以下代码:
import Foundation // required for String(format: _, _)
print(String(format: "a float number: %.2f", 1.0321))
将输出:
a float number: 1.03
一个更优雅和通用的解决方案是重写ruby / python %操作符:
// Updated for beta 5
func %(format:String, args:[CVarArgType]) -> String {
return NSString(format:format, arguments:getVaList(args))
}
"Hello %@, This is pi : %.2f" % ["World", M_PI]
也用于四舍五入:
extension Float
{
func format(f: String) -> String
{
return NSString(format: "%\(f)f", self)
}
mutating func roundTo(f: String)
{
self = NSString(format: "%\(f)f", self).floatValue
}
}
extension Double
{
func format(f: String) -> String
{
return NSString(format: "%\(f)f", self)
}
mutating func roundTo(f: String)
{
self = NSString(format: "%\(f)f", self).doubleValue
}
}
x = 0.90695652173913
x.roundTo(".2")
println(x) //0.91
Swift 4 Xcode 10更新
extension Double {
var asNumber:String {
if self >= 0 {
let formatter = NumberFormatter()
formatter.numberStyle = .none
formatter.percentSymbol = ""
formatter.maximumFractionDigits = 2
return "\(formatter.string(from: NSNumber(value: self)) ?? "")"
}
return ""
}
}
