hey guys, I have some problem with storing the input number as integer in swiftui. i have already declared num as 0 and I wish the input number stored on num but the text always show 0, seems data didnt store on num. How to fix it? Many thanks

var num = 0 VStack {

            TextField("Please Enter your cost in HKD", value: $cost, formatter: NumberFormatter())

                .keyboardType(.numberPad)

                .padding()

                    .overlay(RoundedRectangle(cornerRadius: 100).stroke(Color.blue, lineWidth: 1))

                    //.keyboardType(.numberPad)

                    //.padding()

                 Button("Store Cost")

                        {

                    num = Int(cost)

                 }

            Text("\(num*3)")

              }

Hi @him1202

Your num (number) variable need to be @State and not in the body of View. You are converting from a string to a Int therefore you need to handle that. I have just used nil coalescing however you should tell user that entered incorrect format. You do have an extra call in TextField of formatter: NumberFormatter() See below

struct ContentView: View {
    @State var cost = ""
    @State var number = 0

    var body: some View {
        VStack {
            TextField("Please Enter your cost in HKD", text: $cost)
                .keyboardType(.decimalPad)
                .padding(10)
                .overlay(
                    RoundedRectangle(cornerRadius: 100)
                        .stroke(Color.blue, lineWidth: 1)
                )
                .padding()
            Button("Calculate") {
                number = Int(cost) ?? 0
            }
            .padding()
            .background(Color.blue)
            .foregroundColor(.primary)
            .cornerRadius(30)

            Text("\(number * 3)")
                .padding()
                .font(.largeTitle)
        }
    }
}

However I might do something like this

struct ContentView: View {
    @State var cost = ""

    var number: String {
        guard let cost = Int(cost) else {
            return "Use numbers only"
        }

        return String(cost * 3)
    }

    var body: some View {
        VStack {
            TextField("Please Enter your cost in HKD", text: $cost)
                .keyboardType(.decimalPad)
                .padding(10)
                .overlay(
                    RoundedRectangle(cornerRadius: 100)
                        .stroke(Color.blue, lineWidth: 1)
                )
                .padding()

            Text(number)
                .padding()
                .font(.largeTitle)
        }
    }
}

Thanks for your help, I learned a lot

You may also wish to consider using the currency format.

/// If a number returns it as a Double type
extension String {
    func toDouble() -> Double? {
        return NumberFormatter().number(from: self)?.doubleValue
    }
}

let currencyFormat: NumberFormatter = {
    let currencyFormat = NumberFormatter()
    currencyFormat.numberStyle = .currency

    return currencyFormat
}()

func cashFormat (amount: Double) -> String {   // Double as some currencies have fractional units - dollars & cents, pounds & pence
    return currencyFormat.string(from: NSNumber(value: amount))!
}

Text("\cashFormat(amount: number.toDouble() ?? 0.0)" )   // nil coalescing as 'number' may not actually be a number
     .padding()
     .font(.largeTitle)