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!
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
延伸的力量
extension Double {
var asNumber:String {
if self >= 0 {
var formatter = NSNumberFormatter()
formatter.numberStyle = .NoStyle
formatter.percentSymbol = ""
formatter.maximumFractionDigits = 1
return "\(formatter.stringFromNumber(self)!)"
}
return ""
}
}
let velocity:Float = 12.32982342034
println("The velocity is \(velocity.toNumber)")
输出: 速度是12.3
其他回答
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
iOS 15+版本推荐:
2.31234.formatted(.number.precision(.fractionLength(1)))
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 ""
}
}
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
那么Double和CGFloat类型的扩展呢?
extension Double {
func formatted(_ decimalPlaces: Int?) -> String {
let theDecimalPlaces : Int
if decimalPlaces != nil {
theDecimalPlaces = decimalPlaces!
}
else {
theDecimalPlaces = 2
}
let theNumberFormatter = NumberFormatter()
theNumberFormatter.formatterBehavior = .behavior10_4
theNumberFormatter.minimumIntegerDigits = 1
theNumberFormatter.minimumFractionDigits = 1
theNumberFormatter.maximumFractionDigits = theDecimalPlaces
theNumberFormatter.usesGroupingSeparator = true
theNumberFormatter.groupingSeparator = " "
theNumberFormatter.groupingSize = 3
if let theResult = theNumberFormatter.string(from: NSNumber(value:self)) {
return theResult
}
else {
return "\(self)"
}
}
}
用法:
let aNumber: Double = 112465848348508.458758344
Swift.print("The number: \(aNumber.formatted(2))")
打印:112 465 848 348 508.46