SwiftUI Documentsといふもの 〜 Mac系のファイル操作アプリ作成に便利だった

import SwiftUI

@main
struct SampleDocumentApp: App {
    var fileProvider: FileProvider = FileProvider()
    
    var body: some Scene {
        DocumentGroup(newDocument: SampleDocumentDocument()) { file in
            let _ = print("\(String(describing: file.fileURL))")
            ContentView(document: file.$document)
                .environment(fileProvider)
        }
    }
}

import SwiftUI
import UniformTypeIdentifiers

extension UTType {
    static var exampleText: UTType {
        UTType(importedAs: "com.example.plain-text")
    }
    static var csv: UTType {
        UTType(importedAs: "org.m7e.plain-text")
    }
}

struct SampleDocumentDocument: FileDocument {
    var text: String

    init(text: String = "Hello, world!") {
        self.text = text
    }

    static var readableContentTypes: [UTType] { [.exampleText, .csv] }

    init(configuration: ReadConfiguration) throws {
        guard let data = configuration.file.regularFileContents,
              let string = String(data: data, encoding: .utf8)
        else {
            throw CocoaError(.fileReadCorruptFile)
        }
        text = string
    }
    
    func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
        let data = text.data(using: .utf8)!
        return .init(regularFileWithContents: data)
    }
}

import Foundation

@Observable
class FileProvider {
    var fileName: String = "sample.txt"
    private var myiCloudContainerURL: URL?
    private var isiCouldAvalable: Bool = false
    private var myLocalContainerURL: URL?
    
    init?() {
        guard FileManager.default.ubiquityIdentityToken != nil else {
            return nil
        }
        DispatchQueue.global().async {
            let ubiquityContainerID = "com.apple.CloudDocs"
            if let url = FileManager.default.url(forUbiquityContainerIdentifier: ubiquityContainerID) {
                DispatchQueue.main.async {
                    print("container URL: \(url)")
                    self.myiCloudContainerURL = url
                    self.isiCouldAvalable = true
                    print("iCould is avaialble.")
                }
                return
            }
            print("Error to retrieve iCloud container URL!!!")
        }
        self.myLocalContainerURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
        let error = "Local URL error"
        print("Local URL \(self.myLocalContainerURL?.absoluteString ?? error)")
        
    }
    
    func save(content: String) {
        if isiCouldAvalable {
            let filePath = self.myiCloudContainerURL?.appendingPathComponent(self.fileName)
            do {
                try content.write(to: filePath!, atomically: true, encoding: .utf8)
                print("Success!! \(String(describing: filePath))")
            } catch {
                fatalError("Save iCloud FATAL ERROR!!! \(error)")
            }
        }
        let filePath = self.myLocalContainerURL?.appendingPathComponent("local.csv")
        do {
            try content.write(to: filePath!, atomically: true, encoding: .utf8)
            print("Success!! \(String(describing: filePath))")
        } catch {
            fatalError("Save Local FATAL ERROR!!! \(error)")
        }
    }
    
    func load(fileName: String) -> String {
        if isiCouldAvalable {
            let filePath = self.myiCloudContainerURL?.appendingPathComponent(fileName)
            guard let content = try? String(String(contentsOf: filePath!, encoding: .utf8)) else {
                fatalError("Read FATAL ERROR!!!")
            }
            return content
        }
        return "load Error!!"
    }
}