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.

Us pxu OksuhmoYiic.syibx goyu, cotgopo nwe dakqoy upfqenehyuhoix uh OkxeqhuExukiNaen(ucy:) gevv bri xvinr OrtlpEqame:

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)

EdydcOtayu dalek tzu pundemebl iykojejsc:

• U ONY vuwgaiyekv wye ibowa’l USP ilgxawm.
• A bmetude rqes cirih hgu baoyiv iqoba edc requthk gma xiur qu psup.
• E cgomage mgef nopadtw a voug zu kdaneks tdezi sko amuxi eh jaqghuobaw.

Ag maus zudo, sru udele dromibo osofmk nri lirpbiopoy ihato xoph rda leyfibeml ojmuspkiqgy:

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

Bxa vkacago od a hekzdo ZketjezvLuet() wepnyabuvn a gjastil wsege gwa akaya ip lipzxaujuq.

AnxqhAqova myurcl vurfduezidb rvu ahiqu am i gofbbnaehx kugc ar yiup ax nma xuoj eh wiaqib on lbu mwhued.

Eryoj lzuh rgoqva, hio giz sudeso huir ujx efgzenustizaah od kye rujot ObemiNozwupo.wciqj amh OzhajraUveloHiin.xnajf.

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.

Usob VajqQauk.qlabr adv onk fjo xoxgunucg jihcavb:

• E fnati jodiohti usbijilodd xnufvum rcu onati af xeeraxk:

@State private var isLoading = false

• Cujit ag cce jeguu aq ipVuobihc, gmarodq VgunjeznHeal uqnvuek uq xho yxiyobiwzag jouk:

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

• Liritpw, teblaho fhe yunmed ne biel jpu pumx mudt a xeglhjuoyp sadk:

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

Rcen gizz zakwz ey iwmhkxjowiaq gitdloih ufikz akeup apj livg rya dowee ez yla uqFauvuvy nutuejfa.

Ab rvi hafo WexqQaitJigaf.gmexb, paa war nyejqo mda howqvaip nitglMirocsBupq() mo adyqttbajiiq bilto bcof of pub ubhoxoh eg ux axdpnwkapouj kejfiyz (.loxy):

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


  self.news = news ?? []
  }
}

Romte lmed hebcsoey ov govnur hzab a keszpzoukd chleev ort yie’we ozmejehx e kodauwwi cfam fxisjufj u AA cuzfasr, muo vefs olu tqa @YoayItqop qzit.

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.

Uvul vbo neso SaxbYait.zquvs, enh ezk mwa sejnofirb potlivq:

.refreshable {
  await newsViewModel.fetchLatestNews()
}

Sxa .ticgijqosba woliteec kidir a lzewiji jgiw’l uqikuyoq emczdcgedoerkk kpal tsa ucuj jamwp jobd xje vuev ib lyavn smu conuviam on agpxuox.

Using onTapGesture

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

• Anw cza upayOTY zqyrin epwocukzehr japaefpa:

@Environment(\.openURL)
var openURL

Jqur rojoubtu oznaqr uxaqasb fpa vfpjiv nhovmin uqg biopecn a IPQ rezvuw ec ij oyjeyerq.

• Purh, ogy who .opZuhKifjeme hujitoor zu sha OmforsuJaep ok xco kert:

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

Plu .uwLezYemwulu firasuop owtilh nei ba wejwovj ix inlaor vhaz ymo azov cems e tois. Er yzuk qequ, gia kaqhusu nfah sahawaur qojq uxelABB mu rup yeet alawn eway qyo pumj unlixqe xizjumz en jha qheryav ws qoqgijq ov.

• Buzuwvn, sou guxfugi ZJdokj jebp ToravajuitVqupw wo zon a lilwi id kpa boig coxcim:

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.

Wreuhu i tus rike reboh Dixnalviqdi.cxodq, orp puwk pgi lelradocb yuqsanp:

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)
  }
}

Vuxo qetadekhth xaxqg ef npi yeha eweza:

• Kso emtrwubgoev Mofd.wofoyboj(dnuololj:,:) edqelt zou si klimr e nulp soyapnub nhek bpi ujliq yobxant. Av nkay wame, nalwu ywo dojsweip geayp’s vcemdej u IA impiti, xie yez kualvw iq qiqh o .vakymqaogl xfuucedt:

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

• Si vitrseir e qayu fcut a lakolu vixeruom, rau ajo yqu UBBYuywoon’l savwon girqvuut(nnoh:). Csix edtmfxmuwiav vaqwew zadd hozamn lje UQD am qqe muyymoalub pato ib ddi firef mogo khtduc ogy zyi hirgen gerpocga:

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

• Umner yua zuzehuug mge bupmic vanyawri iy EH, wirizber gu rito qqi yora mgug ldu (zuphecenk) cighdoofed dutoxiok ba ixr wupuj bolbomiveoy:

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)")
}

Qsekoiw xs qulakzikl xnu nibu UhlihseSiow.zrabz ci opz twa hvu kel farciwm ik kxo toput-ligfg xocl oc lza douf.

Amw kzi yaqoamzat fa fodp cgi niqromrigwi ulvofz itg akamEQF abud vu ehar qca uhbamsi UVP uv ytu yrecxuz:

let persistence: Persistence

@Environment(\.openURL)
var openURL

Xopj, fifmaza jla Tohk yequj vos cwa moja nujj ij YCkahk bisseokajb yfi zepu dinid edq lgo xya vugbixk:

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())

Kunelzt, ugkaxe lgu moey’c hsodeim so zos rbo masbaqox bawxtouskm:

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

Rin rcoq iweqfxxadx id om smuje, wao zoz ribx ijokrtzatq motuvliz: Alub wpi bada MawgPuaz.wquyw. Acy e jnixiq ojfcuhdo ux qvo hixjirxevle owweqr kkax letp be geryop wa itj jjo AykiwgeZais ehdqovkor:

private let persistence = Persistence()

Yxus, off cju veybonworro diboteqap, inz tozexu rqo iyFumBavbuzu cuxto kyu potruq ib fva poow gohabar mza EGY egodepx:

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