The task View Modifier (SwiftUI)

.task starts an async task tied to the view's lifecycle: SwiftUI cancels it through cooperative cancellation when the view disappears. The id: variant restarts it on data changes, which makes debounced search a three-line pattern.

Lifecycle-Bound Async Work

Attach .task and the work starts when the view appears and cancels when it leaves.

List(store.products) { product in
  NavigationLink(product.id.uuidString) { Text(product.id.uuidString) }
}
.task {
  await store.fetchProducts()
}

Cancellation is cooperative: Task.sleep throws CancellationError when the task cancels mid-sleep, and long loops should check Task.isCancelled. The default priority is .userInitiated; pass a lower one for background work.

.task(priority: .utility) {
  await store.fetchProducts()
}

task(id:) Restarts on Data Changes

.task(id:) observes an Equatable value. On every change SwiftUI cancels the running task and starts a fresh one with the new value.

.searchable(text: $query)
.task(id: query) {
  await store.search(matching: query)
}

Debounce With Sleep Plus Cancellation

Sleep before the request. If the user types again inside the window, SwiftUI cancels the sleeping task, so no request fires for stale queries.

.task(id: query) {
  do {
    try await Task.sleep(nanoseconds: 300_000_000)
    await store.search(matching: query)
  } catch {
    // cancelled before the request fired
  }
}

A Reusable Debouncing Modifier

Wrap the pattern once and call it as .task(id:nanoseconds:).

struct DebouncingTaskViewModifier<ID: Equatable>: ViewModifier {
  let id: ID
  let priority: TaskPriority
  let nanoseconds: UInt64
  let task: @Sendable () async -> Void

  func body(content: Content) -> some View {
    content.task(id: id, priority: priority) {
      do {
        try await Task.sleep(nanoseconds: nanoseconds)
        await task()
      } catch {
        // ignore cancellation
      }
    }
  }
}

extension View {
  func task<ID: Equatable>(
    id: ID,
    priority: TaskPriority = .userInitiated,
    nanoseconds: UInt64 = 0,
    task: @Sendable @escaping () async -> Void
  ) -> some View {
    modifier(DebouncingTaskViewModifier(id: id, priority: priority, nanoseconds: nanoseconds, task: task))
  }
}

// call site
.task(id: query, nanoseconds: 300_000_000) {
  await store.search(matching: query)
}