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
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
其他回答
这是一种非常快速和简单的方法，不需要复杂的解决方案。
let duration = String(format: "%.01f", 3.32323242)
// result = 3.3
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]
iOS 15+版本推荐:
2.31234.formatted(.number.precision(.fractionLength(1)))
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
我找到了String。localizedStringWithFormat工作得很好:
例子:
let value: Float = 0.33333
let unit: String = "mph"
yourUILabel.text = String.localizedStringWithFormat("%.2f %@", value, unit)
