Playing with a combined stepper and text field for entering numeric quantities

ContentView.swift

//
//  ContentView.swift
//  QuantityStepper
//
//  Created by Vikram Kriplaney on 07.11.2019.
//  Copyright © 2019 iPhonso GmbH. All rights reserved.
//

import SwiftUI


extension ClosedRange {
    func clamp(_ value: Bound) -> Bound {
        return self.lowerBound > value ? self.lowerBound
            : self.upperBound < value ? self.upperBound
            : value
    }
}

extension View {
    func endEditing(_ force: Bool = false) {
        UIApplication.shared.windows.forEach { $0.endEditing(force) }
    }
}

struct QuantityStepper: View {
    struct StepperButtonStyle: ViewModifier {
        func body(content: Content) -> some View {
            content
                .foregroundColor(.primary)
                .padding(11)
                .padding(.horizontal, 6)
                .background(Color(.tertiarySystemFill))
                .cornerRadius(8)
        }
    }

    @Binding var value: Int
    var bounds: ClosedRange<Int> = 0...999

    func increment() {
        endEditing()
        value = bounds.clamp(value + 1)
    }

    func decrement() {
        endEditing()
        value = bounds.clamp(value - 1)
    }

    var stringValue: Binding<String> {
        Binding<String>(
            get: { "\(self.value)" },
            set: { self.value = self.bounds.clamp(Int($0) ?? 0) }
        )
    }

    var body: some View {
        HStack(spacing: 4) {
            Image(systemName: "minus")
                .modifier(StepperButtonStyle())
                .onTapGesture(perform: decrement)

            TextField("Qty", text: stringValue)
                .textFieldStyle(RoundedBorderTextFieldStyle())
                .multilineTextAlignment(.center)
                .keyboardType(.numberPad)
                .frame(width: 60)

            Image(systemName: "plus")
                .modifier(StepperButtonStyle())
                .onTapGesture(perform: increment)
        }
    }
}


struct ContentView: View {
    @State var quantities = Array(repeating: 0, count: 16)

    var body: some View {
        NavigationView {
            List(0 ..< quantities.count, id: \.self) { index in
                Text("Product #\(1 + index)")
                Spacer()
                QuantityStepper(value: self.$quantities[index])
            }.navigationBarTitle("Shopping List")
            .navigationBarItems(trailing: Text("\(quantities.reduce(0, +)) items"))
        }
    }

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