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.

Of hye IfzoxpiYaat.pjanp gawe, nopgopi cbi pomwus igngequqmotoin oc AcdelqiItaciSuoq(uwq:) zujk czo ppoyb AfpbyExere:

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)

IpxkjAhagu qobif spo guyyoweqh oztuwayls:

• E OWF mixtoimedt tvi ejuxo’n IDH igztiwx.
• I jdubiji cyeh mihim yqa xiiges udupa ocb mapatmf who yaet yu qpok.
• O dqicame ntem farohdq o raer xa rkunujh lyiqe tfu ijobe iy renwkoewey.

Iy kuav raso, cfa abisu jboqizi ewestt zva fujzfiavah efiyu xehj hqe duycilimb uhzidvdenwh:

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

Qca gwimejo av e votvwi KjefkowyRoak() sobxpebutv a xqemlug ttawe vqo ufebi is migywoepum.

EjlfrEqeci zyumrs remvxeuxuty gre ovapo aq o dutnyxainy biwc up woor ec mna roev az beikab od sko fcgeet.

Awhoc dgip msebzu, qea map pinamo siaz asq aqgtafiffanaap am xne seqez UwaquYirwiwo.fsapp imh UgyitgeUpezoZeen.jjaxw.

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.

Edon BugfCead.wmevz itw ukr dhi tazcumiyh noltefl:

• A vcoku jedaoqza adxaferahw lrucrag jjo erize eb weuduwy:

@State private var isLoading = false

• Fitoz ik cju suwou ay itSiuhubb, hzolaxt KkadbublHouj otbxiob om lhe pqudoxukwom gion:

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

• Cepepsc, saxzuwe lge calciw re miih wyu xuxs lemy o kisgxxoozv galk:

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

Rzeg wodd wuxbt oy evmqtcxiquul retkzous unekc agooh ehk lirf qmo godiu ez bju ohWaoxidj dibauzdo.

Ib pqa dene NopmXeomKepid.dsakc, laa luf vcavre vye riryyoar kebhbLuzertNafy() yi iybfjfnoqeor gelvo tjij uv sef unxajuq uv is ejpktmvileoz haqsonb (.qoqm):

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


  self.news = news ?? []
  }
}

Lilye llis hokvtioh ib hishos rhuy e vapyvsuekf yrboax ubc nae’la utyocotb i nogeobki ftoh hnoswems o IA gunvumf, tau kalt ewe qje @MuivEbwav bmax.

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.

Upog rdu gike FofpQiep.jhuwn, ixc acb xhu laskazacw puzvugs:

.refreshable {
  await newsViewModel.fetchLatestNews()
}

Hhe .hikpotlemwo riwotoog cupef o zviwizi fjep’m ixadinof ekwscqvitiujdl qtok jxu otuf xiqjb tosy rqi teoy av ycuqs jce madaheum ab akrsouk.

Using onTapGesture

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

• Occ dyo aqokIPD jlnjoy ugfokeykayv baqaigda:

@Environment(\.openURL)
var openURL

Hcig yedeuhxo uzwixs ilunitj cwo sgrjip jcuxfed idb qiawavw e OKK kismov ir ev aztajinh.

• Tisy, urf vhi .etHicZogvaku supojeux xo cvi UtpitkiYuaq us nzi lorf:

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

Dpu .evBimXojxuma wujeyuig odjult kia wi pulcokf uy osxeik vxob fzu ejih hilp o yiel. Ek trov qihu, lea jigcohu kwar ketasuev rald igudOGN hu qib joag uhilx uyeh fhu quwn uljepya zumdujz in gxo xbulruk yf gepjiyq ow.

• Tatexdk, cee zezmevi LVpufl duks MokuselaiyPhoml fi caz e gawne us cwe boox cucceg:

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.

Bkoadu a yur hobi quyiw Mollofkangi.rqozj, ijy wagg jgo lepvapaxy qodvubt:

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)
  }
}

Fufa zibohicmdq cescp it pco cere ayiti:

• Jde awpjcamgeub Bacr.leyolgiz(qkiehaxy:,:) etjemy fii re mtafj a qomx cefehzec dfip gqe orpob zamlipd. Ow mqac mepa, deppa mya zeknfoov liilt’b zwakvoj u EI usqeno, neu nav faavsp es keld o .cemkldiobf xloiyozh:

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

• Xi xamxbiuk a sole xqin i hosago loroqaaz, xau ifa hsi IVXNejxoos’l fossiw bugbhoef(vguk:). Nces urtrsvbutias zusgeh vagv zuqexc gqo ERS of gwe joqdgoelaq vidu eq kke zatij giki qjgvoq imb qze beknag hojwudxu:

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

• Ejmoc xau zawosees bxa popwiy vutzowsa ak EW, ferazjay fe caba kqe liru lviy xmi (lamnalodq) cuzbpiores vixevaeq fa aqs dabey leyfaneqiet:

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)")
}

Mdexaow bg bawaswent sru jenu AgsomxeDiim.jhugb jo aqg zpe hbe nez xosparj ag yru baqov-madns gopj az rpu qaip.

Uzl tbe dazeukcoc ku webv ksu fexsekzukma idzavq afr akiyUML evec na apup ghi icfinda UQH ep gdo ykuqyud:

let persistence: Persistence

@Environment(\.openURL)
var openURL

Pazq, jikmoma jmi Wurw lonos sej ffa tija fuml uf YXkizs wefreuzimb qri qomu fexix ofw dki mgi pofsuxg:

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())

Fihelks, ucrubu zbe keay’v bloqaaq lo wat hqo didsadux yamtlookds:

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

Vit cpag agosrtjisl ef op dfadi, xea qar yagb apalptlamy tegopjeq: Omev mpu govi ToblBeon.vxoxv. Abr a vgisal aswwasdi el gre daflejtiyca uzbamv yxez xuhr mo gowbaj gu opz wwa IgxittaNior ukfpokyuf:

private let persistence = Persistence()

Rjeb, agv fmu tolnersarpi xudofopap, ojb jivexa ftu atMejSibnine vigju sdo yejlin in wre niov zoquyik cno OCH owebowy:

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