[SwiftUI] SwiftUI から PHPicker を使用する方法

func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult])

//
//  SwiftUIPHPicker.swift
//
//  Created by : Tomoaki Yagishita on 2020/12/07
//  © 2020  SmallDeskSoftware
//

import Foundation
import SwiftUI
import PhotosUI
import os

public typealias PHPickerViewCompletionHandler = ( ([PHPickerResult]) -> Void)

public struct SwiftUIPHPicker: UIViewControllerRepresentable {
    // 1
    var configuration: PHPickerConfiguration
    // 2
    var completionHandler: PHPickerViewCompletionHandler?
    
    let logger = Logger(subsystem: "com.smalldesksoftware.SwiftUIPHPicker", category: "SwiftUIPHPicker")
    
    public init(configuration: PHPickerConfiguration, completion: PHPickerViewCompletionHandler? = nil) {
        self.configuration = configuration
        self.completionHandler = completion
    }
    
    public func makeCoordinator() -> Coordinator {
        logger.debug("makeCoordinator called")
        return Coordinator(self)
    }
    //(3)
    public func makeUIViewController(context: Context) -> PHPickerViewController {
        logger.debug("makeUIViewController called")
        let viewController = PHPickerViewController(configuration: configuration)
        viewController.delegate = context.coordinator
        return viewController
    }
    
    //(4)
    public func updateUIViewController(_ uiViewController: PHPickerViewController, context: Context) {
        logger.debug("updateUIViewController called")
    }
    
    
    public class Coordinator : PHPickerViewControllerDelegate {
        let parent: SwiftUIPHPicker
        
        init(_ parent: SwiftUIPHPicker) {
            self.parent = parent
        }
        //(5)
        public func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]) {
            parent.logger.debug("didFinishPicking called")
            picker.dismiss(animated: true)
            // (6)
            self.parent.completionHandler?(results)
        }
    }

}

//
//  ContentView.swift
//
//  Created by : Tomoaki Yagishita on 2020/12/07
//  © 2020  SmallDeskSoftware
//

import SwiftUI
import PhotosUI
import os
import SwiftUIPHPicker

struct ContentView: View {
    // (1)
    @State private var images:[UIImage] = []
    // (2)
    @State private var showPHPicker:Bool = false
    // (3)
    static var config: PHPickerConfiguration {
        var config = PHPickerConfiguration()
        config.filter = .images
        return config
    }
    let logger = Logger(subsystem: "com.smalldesksoftware.PHPickerSample", category: "PHPickerSample")

    var columns: [GridItem] = Array(repeating: .init(.fixed(100)), count: 3)
    var body: some View {
        VStack {
            HStack {
                Spacer()
                Button(action: {
                    showPHPicker.toggle()
                }, label: {
                    Image(systemName: "plus")
                        .font(.largeTitle)
                })
            }
            .padding()
            Spacer()
            LazyVGrid(columns: columns) {
                ForEach(images, id: \.self) { image in
                    Image(uiImage: image)
                        .resizable().scaledToFit()
                }
            }
            .padding()
            Spacer()
        }
        .sheet(isPresented: $showPHPicker) {
            // (4)
            SwiftUIPHPicker(configuration: ContentView.config) { results in
                for result in results {
                    let itemProvider = result.itemProvider
                    if itemProvider.canLoadObject(ofClass: UIImage.self) {
                        itemProvider.loadObject(ofClass: UIImage.self) { image, error in
                            if let image = image as? UIImage {
                                DispatchQueue.main.async {
                                    // (5)
                                    self.images.append(image)
                                }
                            }
                            if let error = error {
                                logger.error("\(error.localizedDescription)")
                            }
                        }
                    }
                }
            }
        }
    }
}