.task 修饰器
在视图出现时加载数据。
.task 修饰器 是 CoddyKit 上的免费 SwiftUI Academy 课时。 这是第 3 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 SwiftUI Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 SwiftUI Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Loading When a View Appears
Often you want to fetch data the moment a screen shows. The .task modifier runs async work exactly when the view appears. ⏱️
Attaching .task
Add .task to any view and give it an async closure. SwiftUI starts that work as the view comes on screen.
List(users) { user in Text(user.name) }
.task { await load() }It Calls Async Code
Inside .task you can freely use await. That makes it the natural home for your URLSession fetch on appearance.
.task {
users = try? await loadUsers()
}Why Not onAppear
The older onAppear cannot await async work directly. The .task modifier is built for concurrency, so prefer it for loading.
Automatic Cancellation
When the view disappears, SwiftUI cancels the task for you. That stops wasted work and avoids updating a gone view. ✨
Reacting to an id
Pass an id to .task and it reruns whenever that value changes. Perfect for reloading when a selection updates.
.task(id: selectedID) {
await loadDetail(selectedID)
}Updating State After Fetch
Store results in @State so assigning them refreshes the UI. The view redraws as soon as the data arrives.
@State private var users: [User] = []Handling Errors Inside
Wrap risky calls in do/catch inside the task. You can then set an error message that the view shows the user.
do { users = try await loadUsers() }
catch { errorText = "Failed" }Runs on the Main Actor
A .task closure starts on the main actor, so updating state and UI from it is safe without extra hopping.
One Task per Lifetime
By default .task runs once per appearance. For repeated refresh use pull-to-refresh or a changing id instead.
Keeping the Closure Small
Call a named function from .task rather than stuffing logic inline. It keeps the view tidy and easy to read.
.task { await viewModel.refresh() }Quick Check
Quick check on triggering async loads.
Recap: .task
You learned that .task runs async work when a view appears, cancels on disappear, can rerun on an id, and is the go-to place to fetch. 👍
常见问题解答
「.task 修饰器」课时是免费的吗？
是的 — 「.task 修饰器」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 SwiftUI Academy 课程的其余内容，请升级到 CoddyKit PRO。 SwiftUI Academy 课程共包含 4 节课。
「.task 修饰器」这节课中我会学到什么？
在视图出现时加载数据。 你通过在浏览器中直接运行的动手代码来练习 SwiftUI Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 SwiftUI Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 SwiftUI Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 3 节课，共 4 节。
「.task 修饰器」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 SwiftUI Academy 课中编写并运行代码吗？
能。每节 SwiftUI Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。