新增一个Swift文件

    1. public class DoubleFormatter: Formatter {
    3.     override public func string(for obj: Any?) -> String? {
    4.         var retVal: String?
    5.         let formatter = NumberFormatter()
    6.         formatter.numberStyle = .decimal
    8.         if let dbl = obj as? Double {
    9.             retVal = formatter.string(from: NSNumber(value: dbl))
    10.         } else {
    11.             retVal = nil
    12.         }
    14.         return retVal
    15.     }
    17.     override public func getObjectValue(_ obj: AutoreleasingUnsafeMutablePointer<AnyObject?>?, for string: String, errorDescription error: AutoreleasingUnsafeMutablePointer<NSString?>?) -> Bool {
    19.         var retVal = true
    21.         if let dbl = Double(string), let objok = obj {
    22.             objok.pointee = dbl as AnyObject?
    23.             retVal = true
    24.         } else {
    25.             retVal = false
    26.         }
    28.         return retVal
    30.     }
    31. }

    用法

       TextField("enter",value:$double,formatter: DoubleFormatter())
           .textFieldStyle(RoundedBorderTextFieldStyle())
           .keyboardType(.decimalPad)