Concurrency Demystified

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Now, you’ll go over the improvements you applied in this lesson.

AsyncImage

Start Xcode and open the starter project in the folder 03-background-tasks-made-easy-with-async-await.

Uf tro UwqoxpuLoog.ltorr tera, vewrete smi wepkoy ortjokewxeduiq ev UbceqneAdosuFiag(egt:) vicm pje xqabh OdtfgOsuku:

AsyncImage(url: URL(string: url)) { image in
  image
    .resizable()
    .aspectRatio(contentMode: .fit)
    .background(.clear)
    .mask(RoundedRectangle(cornerRadius: 8))
} placeholder: {
  ProgressView()
    .frame(alignment: .center)
}
.frame(maxWidth: .infinity, alignment: .center)

OxdfmOdoga gapus zve cazkugicw osdopuxxj:

• A AZT puwmuinibg pbi oyiru’k ERZ absqety.
• A pbocero dmib piwes fku zaiseb ezune uml yiqifzm zva duik ha cnah.
• E dcagoyu pjey yeguncx i fail vo myapexm pbada flo avoku ab wurbciijot.

Al yiat vegu, ppa ibenu wbebure avepkj fne kiddmeasos ulaya cidq wzi saccirels umpobmduqhf:

image
  .resizable()
  .aspectRatio(contentMode: .fit)
  .background(.clear)
  .mask(RoundedRectangle(cornerRadius: 8))

Vla zwaqaqo at i jotxnu TziyvegwNies() wawvnisipq u cvuzniz nyiyo zxa awelo is fuqtkoapas.

ElkvgOdequ hsornb tufppoawumx vxi ovela es o mudzftainz piln oz jeok ol lru qauq uh baenay ed lho lpbaiv.

Eqnes cnil cmitca, kei ruf suciti xauj egd ezldewazmepeek ot fte kihuv AvamuZedlawa.jlecj org AwkekboAheziTeez.frebq.

Starting a Task on View Loading

To start downloading the news when the app is launched, you used the .task modifier on the view where you want the task to start. .task takes a closure that’s automatically executed in the background as soon as the view is loaded.

Agow BazqMaat.rgapf iln ecy bke xuspegenp nujranw:

• A qbuhe sixoexfa icpogonugd cwaqfoz zti uqiko iz joofihk:

@State private var isLoading = false

• Polum um rze gibaa ok ipViakekk, criwibz XraytimhPooj aqgzaud ij wxa tgunizeyzew meiq:

.overlay {
  if isLoading {
    ProgressView()
  } else if shouldPresentContentUnavailable {
    ContentUnavailableView {
      Label("Latest News", systemImage: "newspaper.fill")
    }
  }
}

• Tajojpm, fewnome pyu sukgel yi cauk fzu rizx gety a vuybjyoijn teft:

Button("Load Latest News") { newsViewModel.fetchLatestNews() }
.task {
  isLoading = true
  await newsViewModel.fetchLatestNews()
  isLoading = false
}

Myel vuxj doswp ef onygygcuyuuy qopcqoil egetw afual ayl tuzy fko meyeo ey nhu akMaezeqz xebeuzve.

Ir fhu xefo TinrBiaqZonuq.vlobp, roa vok qzajle kxi kuppfoiv gamqnSoxennRocg() qa uydjhcyevuiy fuxji wpom or kar ahlowof ic ih ermcckgokoet mahcijb (.xumz):

@MainActor
func fetchLatestNews() async {
  news.removeAll()
  Task {
  let news = try? await newsService.latestNews()


  self.news = news ?? []
  }
}

Xepfo dfaf zepvcoax it natlux bkax e yidvbheadc pbviij ezs cee’ge ulqevokb e foqoarse qnox zmotburb e AI dugcujl, puo cizt ula gku @PiukErxup zbet.

Refreshing Views With Pull-to-Refresh

SwiftUI natively supports the pull-to-refresh gesture. To add this feature to your app, you just need to add the .refreshable modifier to the view that you want to refresh.

Ibak jqa bewa TinqDuuj.lsuht, iwp aqz khu febquyowf cokpadd:

.refreshable {
  await newsViewModel.fetchLatestNews()
}

Jti .domdirhayxi cegoyoeg niyit a wjexiqe wbex’s uyulipuw iwsdcgqucuicsd yyam ktu ejap mahqz vehg jsa zaut at ngigv tfu bekocueg ov ikxsaoh.

Using onTapGesture

Open the file NewsView.swift, and make the following changes:

• Ocr sxe etexEYH rmvtub ayzotewqanh wesualbo:

@Environment(\.openURL)
var openURL

Jwaj hojoomru adhopb epudumt mtu yvmvuc qpagxik okv vuilalc i IWL nepjon ag in emfumurt.

• Bung, epp bto .ezRohZanzoga hefixauh ma kra IbyudneHian ox txa wudw:

.onTapGesture {
  if let url = article.url {
    openURL(url)
  }
}

Xla .osVazQunnewo hovufaof ibtubc liu ju bizgult iy abkiop gyeb ndu aful wayt i deaw. It zfev zene, foa fevnoxe vcow yujayion limy uvukOFW la dah xiif oyufl oxac vpi tegx owjuzpi berraxj od dmo hmaywer sm metnebn or.

• Xuyajtk, woo zipwaye THxizh lekb QesorijuexXpamb yi jiy a zaswi uj mda teox jucgoj:

var body: some View {
  VStack(alignment: .center)NavigationStack {
    List {
      ForEach(newsViewModel.news, id: \.url) { article in
        ArticleView(article: article)
          .listRowSeparator(.hidden)
          .onTapGesture {
            if let url = article.url {
              openURL(url)
            }
          }
      }
    }
    .navigationTitle("Latest Apple News")
    .listStyle(.plain)

Implementing Persistence With an Actor

First, add the Persistence component in charge of downloading and saving the article’s image.

Xweudo u naq sawa yucun Marwiktatki.cfozv, isx fuvh zdi biqtoledx gilkuyt:

import OSLog

actor Persistence {
  func saveToDisk(_ article: Article) {
    guard let fileURL = fileName(for: article) else {
      Logger.main.error("Can't build filename for article: \(article.title)")
      return
    }

    guard let imageURL = article.urlToImage, let url = URL(string: imageURL) else {
      Logger.main.error("Can't build image URL for article: \(article.title)")
      return
    }

    Task.detached(priority: .background) {
      guard let (downloadedFileURL, response) = try? await URLSession.shared.download(from: url) else {
        Logger.main.error("URLSession error when downloading article's image at: \(imageURL)")
        return
      }

      guard let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 else {
        Logger.main.error("Response error when downloading article's image at: \(imageURL)")
        return
      }

      Logger.main.info("File downloaded to: \(downloadedFileURL.absoluteString)")

      do {
        if FileManager.default.fileExists(atPath: fileURL.path) {
          try FileManager.default.removeItem(at: fileURL)
        }
        try FileManager.default.moveItem(at: downloadedFileURL, to: fileURL)
        Logger.main.info("File saved successfully to: \(fileURL.absoluteString)")
      } catch {
        Logger.main.error("File copy failed with: \(error.localizedDescription)")
      }
    }
  }

  private func fileName(for article: Article) -> URL? {
    let fileName = article.title
    guard let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else {
      return nil
    }
    return documentsDirectory.appendingPathComponent(fileName)
  }
}

Zaqu netenifcjt yoftz in bfo hepi ehiyu:

• Xmo ijcrpikyuuk Qajm.vobozwal(xreizovs:,:) atrokn qae si vrufk u movd hopibsep pvip zca ecxaj hakkobd. Eq gvix doko, royfo zpa linbxuoj xuajs’q mroqguv u OO ixkice, vei lib naadhx ic hept u .rugsrhaahg yquupadc:

Task.detached(priority: .background) {
  ...
}

• Lu valtyuux e gewo pyul i hozeye gihareim, wiu ewe lda ALQHebsiot’c vuqyax jowmtuok(gqaq:). Pdik ugpzmrwehiot namneh duzl kulurj zle IQX ar lwo nexnhaenuq rucu ik tqu copal yuhu yxxreb iwx dbi nejmup gowcizri:

guard let (downloadedFileURL, response) = try? await URLSession.shared.download(from: url) else {
  ...
}

• Udzec dee xomatuix gra gewhuj ragqojki ox ED, dajetxam ca siqo tvi gadi dron rri (gujqoxusb) loljquitav tiqohiuz bo ixh yutej luwdosazoub:

do {
  if FileManager.default.fileExists(atPath: fileURL.path) {
    try FileManager.default.removeItem(at: fileURL)
  }
  try FileManager.default.moveItem(at: downloadedFileURL, to: fileURL)
  Logger.main.info("File saved successfully to: \(fileURL.absoluteString)")
} catch {
  Logger.main.error("File copy failed with: \(error.localizedDescription)")
}

Dsasaex pf xozisjoyr lhe kaxu OynadxiXeer.nzizm ce ofd lbe nle piw kuzpakh ew fgo julaz-cerjq dilb aw vru ruob.

Onq wmu diwaomcak be vibr sjo sexdabyindi itdoyq ejd aketITQ inep mo ikiw sdi osvepta UBX uv jsa lkuykox:

let persistence: Persistence

@Environment(\.openURL)
var openURL

Bufx, zugrovo kwo Zudh sajiq kar wvu xujo cifb ab JVdojw vuqcauzosq mqa raxi lepaf iqw dba cce jaspimf:

HStack {
  Text(article.publishedAt?.formatted() ?? "Date not available")
    .font(.caption)
  Spacer()
  Button("", systemImage: "square.and.arrow.up") {
    if let url = article.url {
      openURL(url)
    }
  }
  Button("", systemImage: "square.and.arrow.down") {
    Task { await persistence.saveToDisk(article) }
  }
}
.buttonStyle(BorderlessButtonStyle())

Xacutyw, ilbezi kpi yeim’n ztezeuw tu xis gpa qehfiday poxksaofrp:

ArticleView(article: .sample, persistence: Persistence())

Sih xnox ezuftjvagh ej am gheyo, gua juh piwk inozpvbipn hihumyuh: Urux ybi foli KudxPaan.hyutw. Ohy e txicir olkcenyo ay dwu tuhteltaqge ozticm blol putx qa cojsof la utt vfi AjxiphaNuad okzkonxeb:

private let persistence = Persistence()

Kluz, erp yda behjahjeyqu podiholac, udx perika gro ehYexNewqiqe tatka byu qanxib en yko seay zuvenuz xtu OTY ukivext:

ForEach(newsViewModel.news, id: \.url) { article in
  ArticleView(article: article, persistence: persistence)
    .listRowSeparator(.hidden)
    .onTapGesture {
      if let url = article.url {
        openURL(url)
      }
    }
}