[Xcode/SwiftUI] SwiftUIで数字を英語の単語に変換する方法【NumberFormatter活用】

import SwiftUI

struct HomeView: View {
    @State private var input: String = ""
    @State private var spelledOut: String = ""

    var body: some View {
        VStack(spacing: 32) {
            TextField("Enter a number", text: $input)
                .keyboardType(.numberPad)
                .font(.system(size: 24))
                .padding()
                .background(Color(.systemGray6))
                .cornerRadius(12)
                .padding(.horizontal)
                .onChange(of: input) {
                    spelledOut = formatNumberAsWords(input)
                }
            Text(spelledOut)
                .font(.title.italic())
                .multilineTextAlignment(.center)
                .padding()
            Spacer()
        }
        .onAppear {
            spelledOut = formatNumberAsWords(input)
        }
    }

    private func formatNumberAsWords(_ input: String) -> String {
        guard let number = Int(input) else { return "Invalid input" }
        let numberFormatter = NumberFormatter()
        numberFormatter.numberStyle = .spellOut // 数値を単語に変換するスタイル
        return numberFormatter.string(from: NSNumber(value: number)) ?? "Invalid input"
    }
}