Day 19 challenge of "100 days of Swift UI" - length converter

ContentView.swift

//
//  ContentView.swift
//  Conversions
//
//  Created by Maarten Engels on 11/10/2019.
//  Copyright © 2019 thedreamweb. All rights reserved.
//

import SwiftUI

struct ContentView: View {
    
    @State var inputAmount = ""
    @State var fromConversionIndex = 1
    @State var toConversionIndex = 3
    
    let units: [(unitName: String, conversionRate: Double)] = [("mm", 0.001), ("m", 1.0), ("km", 1000), ("inch", 0.0254), ("foot", 0.3048), ("yard", 0.9144), ("mile", 1_609.344)]
    
    var inputValue: Double {
        return Double(inputAmount) ?? 0
    }
    
    var unitAmount: Double {
        let unit = units[fromConversionIndex]
        return inputValue * unit.conversionRate
    }
    
    var convertedAmount: Double {
        let unit = units[toConversionIndex]
        return unitAmount / unit.conversionRate
    }
    
    var body: some View {
        NavigationView {
            Form {
                Section(header: Text("Convert")) {
                    TextField("Amount to convert", text: $inputAmount)
                        .keyboardType(.decimalPad)
                    Picker("from unit", selection: $fromConversionIndex) {
                        ForEach(0 ..< units.count) { 
                            Text("\(self.units[$0].unitName)")
                        }
                    }.pickerStyle(SegmentedPickerStyle())
                }
                
                Section(header: Text("To")) {
                    Picker("To unit", selection: $toConversionIndex) {
                        ForEach(0 ..< units.count) {
                            Text("\(self.units[$0].unitName)")
                        }
                    }.pickerStyle(SegmentedPickerStyle())
                }
                
                Section(header: Text("Converted value")) {
                    Text("\(inputValue == 1337 ? "h4x0r!" : String(convertedAmount))")
                }
            }.navigationBarTitle("Conversions")
        }
    }
}

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

This is a simple solution to the first challenge of "100 days of SwiftUI": write a unit conversion application. It's not clever by any means, but at least it has an Easter egg :)