2020.8.9

特定の種類のCodableデータの読み込み
Loading a specific kind of Codable data

2つの異なる種類のJSONをSwift構造体にロード
1つは宇宙飛行士用
もう1つはミッション用
project8-files
astronauts.jsonとMissions.json

astronauts.json

import Foundation

extension Bundle {
    func decode(_ file: String) -> [Astronaut] {
        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([Astronaut].self, from: data) else {
            fatalError("Failed to decode \(file) from bundle.")
        }

        return loaded
    }
}

/-----------------------------------------------------------

import SwiftUI

struct Astronaut: Codable, Identifiable {
    let id: String
    let name: String
    let description: String
}

struct ContentView: View {
    let astronauts = Bundle.main.decode("astronauts.json")
    
    var body: some View {
        Text("\(astronauts.count)")
    }
}

---

ジェネリックを使用してあらゆる種類のCodableデータをロードする
Using generics to load any kind of Codable data

missions.json

struct CrewRole: Codable {
    let name: String
    let role: String
}

struct Mission: Codable, Identifiable {
    let id: Int
    let launchDate: String?
    let crew: [CrewRole]
    let description: String
}

This is called a nested struct

ジェネリック

// Bundle-Decodable.swift
// Moonshot

import Foundation

extension Bundle {
    // ジェネリック版
    func decode<T: Codable>(_ 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
    }

    // 非ジェネリック版
    /*
    func decode(_ file: String) -> [Astronaut] {
        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([Astronaut].self, from: data) else {
            fatalError("Failed to decode \(file) from bundle.")
        }

        return loaded
    }
     */
}

import SwiftUI

//------------------------------------
struct Astronaut: Codable, Identifiable {
    let id: String
    let name: String
    let description: String
}
//------------------------------------
struct Mission: Codable, Identifiable {
    struct CrewRole: Codable {
        let name: String
        let role: String
    }

    let id: Int
    let launchDate: String?
    let crew: [CrewRole]
    let description: String
}

//------------------------------------

struct ContentView: View {
    let astronauts: [Astronaut] = Bundle.main.decode("astronauts.json")
    let missions: [Mission] = Bundle.main.decode("missions.json")
    
    var body: some View {
        Text("\(astronauts.count)")
    }
}

---

ミッションビューのフォーマット
Formatting our mission view

//  Bundle-Decodable.swift

import Foundation

extension Bundle {
    // ジェネリック版
    func decode<T: Codable>(_ 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()
        let formatter = DateFormatter()
        formatter.dateFormat = "y-MM-dd"
        decoder.dateDecodingStrategy = .formatted(formatter)

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

        return loaded
    }

import SwiftUI

//------------------------------------
struct Astronaut: Codable, Identifiable {
    let id: String
    let name: String
    let description: String
}
//------------------------------------
struct Mission: Codable, Identifiable {
        struct CrewRole: Codable {
            let name: String
            let role: String
        }

    let id: Int
    let launchDate: Date?
    //let launchDate: String?
    let crew: [CrewRole]
    let description: String
    
    //----------------------
    var displayName: String {
        "Apollo \(id)"
    }
    var image: String {
        "apollo\(id)"
    }
    //----------------------
    var formattedLaunchDate: String {
        if let launchDate = launchDate {
            let formatter = DateFormatter()
            formatter.dateStyle = .long
            return formatter.string(from: launchDate)
        } else {
            return "N/A"
        }
    }
}
//------------------------------------
struct ContentView: View {
    let astronauts: [Astronaut] = Bundle.main.decode("astronauts.json")
    let missions: [Mission] = Bundle.main.decode("missions.json")
    
    var body: some View {
        NavigationView {
            List(missions) { mission in
                NavigationLink(destination: Text("Detail view")) {
                    Image(mission.image)
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                        .frame(width: 44, height: 44)

                    VStack(alignment: .leading) {
                        Text(mission.displayName)
                            .font(.headline)
                        //Text(mission.launchDate ?? "N/A")
                        Text(mission.formattedLaunchDate)
                    }
                }
            }
            .navigationBarTitle("Moonshot")
        }
    }
}