Meet Swift Async Algorithms

2:01 - The messaging app

struct Account {
  var messages: AsyncStream<Message>
}  

actor AccountManager {
  var primaryAccount: Account
  var secondaryAccount: Account? 
}

protocol MessagePreview {
  func displayPreviews(_ manager: AccountManager) async
}

3:16 - Zip

// upload attachments of videos and previews such that every video has a preview that are created concurrently so that neither blocks each other. 

for try await (vid, preview) in zip(videos, previews) {
  try await upload(vid, preview)
}

5:09 - Merge

// Display previews of messages from either the primary or secondary account

for try await message in merge(primaryAccount.messages, secondaryAccount.messages) {
  displayPreview(message)
}

6:37 - Suspending Clock

// Sleep until a given deadline

let clock = SuspendingClock()
var deadline = clock.now + .seconds(3)
try await clock.sleep(until: deadline)

6:56 - Suspending Clock vs. Continuous Clock

let clock = SuspendingClock()
let elapsed = await clock.measure {
  await someLongRunningWork()
}
//Elapsed time reads 00:05.40

let clock = ContinuousClock()
let elapsed = await clock.measure {
  await someLongRunningWork()
}
//Elapsed time reads 00:19.54

8:34 - Control searching messages

// Control searching messages

class SearchController {
  let searchResults = AsyncChannel<SearchResult>()

  func search<SearchValues: AsyncSequence>(_ searchValues: SearchValues) 
    where SearchValues.Element == String 
}

9:16 - Debounce

let queries = searchValues
   .debounce(for: .milliseconds(300))

for await query in queries {
  let results = try await performSearch(query)
  await channel.send(results)
}

10:21 - Chunked by

let batches = outboundMessages.chunked(
  by: .repeating(every: .milliseconds(500))
)

let encoder = JSONEncoder() 
for await batch in batches {
  let data = try encoder.encode(batch)
  try await postToServer(data) 
}

11:22 - Conversions in initializers

// Create a message with awaiting attachments to be encoded
init<Attachments: AsyncSequence>(_ attachments: Attachments) async rethrows {
  self.attachments = try await Array(attachments)
}