アイテムの主要なリストを作成する
Building a primary list of items
このアプリでは、Appleのメールアプリやメモアプリと同じように、2つのビューを並べて表示します。

アプリのメインビューを作成することからプロジェクトを開始します。これには、すべてのスキーリゾートのリスト、スキー場の出身国、スキー場の数、スキー場の数が表示されます。 「トレイル」または単に「スロープ」と呼ばれることもあります。

//
//  Resort.swift
//  SnowSeeker

import Foundation

struct Resort: Codable, Identifiable {
    let id: String
    let name: String
    let country: String
    let description: String
    let imageCredit: String
    let price: Int
    let size: Int
    let snowDepth: Int
    let elevation: Int
    let runs: Int
    let facilities: [String]
    
    //Bundle-Decodable.swift関連
    static let allResorts: [Resort] = Bundle.main.decode("resorts.json")
    static let example = allResorts[0]
    //以下も有り
    //static let example = (Bundle.main.decode("resorts.json") as [Resort])[0]
}

//
//  Bundle-Decodable.swift
//  SnowSeeker

import Foundation

extension Bundle {
    func decode<T: Decodable>(_ file: String) -> T {
        guard let url = self.url(forResource: file, withExtension: nil) else {
            fatalError("Failed to locate \(file) in bundle.")
        }

        guard let data = try? Data(contentsOf: url) else {
            fatalError("Failed to load \(file) from bundle.")
        }

        let decoder = JSONDecoder()

        guard let loaded = try? decoder.decode(T.self, from: data) else {
            fatalError("Failed to decode \(file) from bundle.")
        }

        return loaded
    }
}

import SwiftUI


struct ContentView: View {
    let resorts: [Resort] = Bundle.main.decode("resorts.json")

    var body: some View {
        
        NavigationView {
            List(resorts) { resort in
                NavigationLink(destination: Text(resort.name)) {
                    Image(resort.country)
                        .resizable()
                        .scaledToFill()
                        .frame(width: 40, height: 25)
                        .clipShape(
                            RoundedRectangle(cornerRadius: 5)
                        )
                        .overlay(
                            RoundedRectangle(cornerRadius: 5)
                                .stroke(Color.black, lineWidth: 1)
                        )

                    VStack(alignment: .leading) {
                        Text(resort.name)
                            .font(.headline)
                        Text("\(resort.runs) runs")
                            .foregroundColor(.secondary)
                    }
                }
            }
            .navigationBarTitle("Resorts")
        }
        
    }
}

NavigationViewを横向きで機能させる
Making NavigationView work in landscape

NavigationViewのセカンダリビューの作成
Creating a secondary view for NavigationView

//
//  SkiDetailsView.swift
//  SnowSeeker


import SwiftUI

struct SkiDetailsView: View {
    let resort: Resort

    var body: some View {
        VStack {
            Text("Elevation: \(resort.elevation)m")
            Text("Snow: \(resort.snowDepth)cm")
        }
    }
}

struct SkiDetailsView_Previews: PreviewProvider {
    static var previews: some View {
        SkiDetailsView(resort: Resort.example)
    }
}

//
//  ResortDetailsView.swift
//  SnowSeeker
//
//  Created by Naoki Abe on 2020/09/20.
//  Copyright © 2020 Naoki Abe. All rights reserved.
//

import SwiftUI

struct ResortDetailsView: View {
    let resort: Resort
    
//    var size: String {
//        ["Small", "Average", "Large"][resort.size - 1]
//    }
    
    var size: String {
        switch resort.size {
        case 1:
            return "Small"
        case 2:
            return "Average"
        default:
            return "Large"
        }
    }
    
    var price: String {
        String(repeating: "$", count: resort.price)
    }
    
    var body: some View {
        VStack {
            Text("Size: \(size)")
            Text("Price: \(price)")
        }
    }
}

struct ResortDetailsView_Previews: PreviewProvider {
    static var previews: some View {
        ResortDetailsView(resort: Resort.example)
    }
}

//
//  ResortView.swift
//  SnowSeeker

import SwiftUI

struct ResortView: View {
    let resort: Resort

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 0) {
                Image(decorative: resort.id)
                    .resizable()
                    .scaledToFit()

                Group {
                    HStack {
                        Spacer()
                        ResortDetailsView(resort: resort)
                        SkiDetailsView(resort: resort)
                        Spacer()
                    }
                    .font(.headline)
                    .foregroundColor(.secondary)
                    .padding(.top)
                    
                    Text(resort.description)
                        .padding(.vertical)

                    Text("Facilities")
                        .font(.headline)

//                    Text(resort.facilities.joined(separator: ", "))
//                    .padding(.vertical)
                    Text(ListFormatter.localizedString(byJoining: resort.facilities))
                        .padding(.vertical)
                }
                .padding(.horizontal)
            }
        }
        .navigationBarTitle(Text("\(resort.name), \(resort.country)"), displayMode: .inline)
    }
}

struct ResortView_Previews: PreviewProvider {
    static var previews: some View {
        ResortView(resort: Resort.example)
    }
}