BinidingExt.swift

struct ContentView: View {
    let keyboard: UIKeyboardType = .emailAddress
    @State var text = ""
    
    var body: some View {
        Text("Hello, world!")
            .padding()
        TextField("Home", text: $text.limit(by: 10).trim(.numeric))
            .keyboardType(keyboard)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

extension Binding where Value == String {
    func limit(by length: Int = 100) -> Binding<String> {
        if self.wrappedValue.count > length {
            DispatchQueue.main.async {
                self.wrappedValue = String(self.wrappedValue.dropLast())
            }
        }
        return self
    }
    
    func trim(_ type: TrimType = .alphaNumeric) -> Binding<String> {
        DispatchQueue.main.async {
            self.wrappedValue = String(self.wrappedValue.trim(type: type))
        }
        return self
    }
}



enum TrimType {
    case alphaNumeric
    case numeric
}

extension String {
    func trim(type : TrimType) -> String {
        switch type {
        case .alphaNumeric:
            let invalidChars = NSCharacterSet.alphanumerics.inverted
            return self.trimmingCharacters(in: invalidChars)
        case .numeric:
            let allowedCharacters = "1234567890"
            let allowedCharacterSet = CharacterSet(charactersIn: allowedCharacters).inverted
            return self.trimmingCharacters(in: allowedCharacterSet)
        }
    }
}