// 輸出格式化
// 輸出 2位小數(shù)
let b = 12.23823
let format = String(format: "%.2f", b)
print("double:\(format)")? ? ? ? ? ? ? // 1.24
extension Double {
func format(_ f: Int) -> String {
return String(format: "%.\(f)f", self)
}
}
// 保留三位小數(shù)
print("--> double:\(b.format(3))")? //"--> double:12.238\n"