Currency formatter SwiftUI

I'm trying to format as the user inputs a value into the textfield. I have the following code already but I couldn't find a way to do this into the textfield.

import SwiftUI

struct ContentView: View {
    @State private var amount: String = ""
    @State private var formattedAmount: String = ""
 
    var body: some View {
        VStack {
            Text("Valor: \(formattedAmount)")
            
            TextField("Valor", text: $amount)
                .textFieldStyle(.roundedBorder)
                .padding()
                .keyboardType(.numberPad)
                .onChange(of: amount, perform: { value in
                    updateFormattedAmount()
                })
        }
    }

    private func updateFormattedAmount() {
        guard let number = Double(amount) else {
            formattedAmount = ""
            return
        }
        
        let formatter = currencyFormatter
        formattedAmount = formatter.string(from: NSNumber(value: number / 100)) ?? ""
    }

    private var currencyFormatter: NumberFormatter {
        let formatter = NumberFormatter()
        formatter.numberStyle = .currency
        formatter.currencyCode = "BRL"
        formatter.currencySymbol = "R$"
        formatter.minimumFractionDigits = 2
        formatter.maximumFractionDigits = 2
        formatter.groupingSeparator = "."
        formatter.usesGroupingSeparator = true
        return formatter
    }
}

This is what I have on the UI:

I wish to display on the textfield what I've done with formattedAmount var.

I like to use TextField's new format: API, e.g.

struct ContentView: View {
    @State var amount: Decimal = 0 // always use Decimal for money
    @Environment(\.locale) private var locale // body will be called if they change their currency.

    var body: some View {

        TextField("Amount", value: $amount, format: .currency(code: locale.currency?.identifier ?? "USD")                
            
    }
}

or

struct Amount {
    var value: Decimal = 0
    let currencyCode = "USD"
}

struct ContentView: View {
    @State var amount = Amount()

    var body: some View {
        TextField("Amount", value: $amount.value, format: .currency(code: amount.currencyCode)
    }
}

Change

@State private var amount: String = ""

TextField("Valor", text: $amount)

To

@State private var amount: Double = 0.0

TextField("Valor", value: $amount, formatter: currencyFormatter)

Then when the user "submits" it will change the field with all the formatter settings.

yes, the above answer suggested by @lorem ipsum is correct, But the main thing you have to understand is while editing Textfield can reflect those changes once you dismiss the keyboard. And if you want to achieve that you have to write Coordinators for UITextFieldDelegate mostly in shouldChangeCharacterIn API of UITextField. Also the code that you have written, you don't need to write that much to achieve the same. you can directly use Formatter on the TextField API like below code. Pls see the below code. It will work the way you want it, but tapping on done button.

struct ContentView: View {
    @State private var amount: Double = 0.0
    let currencyFormatter: NumberFormatter = {
        let formatter = NumberFormatter()
        formatter.currencyCode = "BRL"
        formatter.currencySymbol = "R$"
        formatter.minimumFractionDigits = 0
        formatter.maximumFractionDigits = 0
        formatter.usesGroupingSeparator = true
        return formatter
    }()
    
    var body: some View {
        VStack {
            Text("Valor: \(amount, specifier: "%.2f")")
            TextField("Valor", value: $amount, format: .currency(code: "BRL"))
                .textFieldStyle(.roundedBorder)
                .padding()
                .keyboardType(.numberPad)
        }
    }
}

Again if you don't need on done button, than review this article, it is the closest approach similar to your question.

How to Use Currency Input in a UITextField. Hope it helps.