SwiftUI Academy · 课时

使用 @FetchRequest 获取数据

将托管对象直接加载到视图中。

使用 @FetchRequest 获取数据 是 CoddyKit 上的免费 SwiftUI Academy 课时。这是第 2 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。

Reading Records in Views

To show saved data, a SwiftUI view needs to fetch it from Core Data and re-render whenever that data changes.

The @FetchRequest Wrapper

The @FetchRequest property wrapper runs a query for an entity and keeps the results live and current for you.

@FetchRequest(sortDescriptors: []) var tasks: FetchedResults<Task>

What You Get Back

Results arrive as FetchedResults, a collection you can loop over just like an array inside your view body.

Showing Them in a List

Drop the results straight into a List with ForEach to render one row per stored record.

List(tasks) { task in
    Text(task.title ?? "Untitled")
}

Sorting the Results

Pass sortDescriptors so rows arrive in a predictable order instead of a random one.

@FetchRequest(sortDescriptors: [SortDescriptor(\.title)]) var tasks: FetchedResults<Task>

Filtering with a Predicate

Add an NSPredicate to fetch only the records that match a rule, like done items or a search term.

@FetchRequest(sortDescriptors: [], predicate: NSPredicate(format: "isDone == true")) var done: FetchedResults<Task>

It Stays Live

@FetchRequest watches the context, so when you add or delete a record the view updates automatically. ⚡

It Needs the Context

@FetchRequest reads the context from the environment, so the value you injected in the stack must be present.

Handling an Empty Result

When the fetch returns nothing, show a friendly empty state instead of a blank screen.

if tasks.isEmpty {
    Text("No tasks yet")
}

Optional Attributes

Core Data attributes are often optional in Swift, so unwrap them safely before you display their values.

Declare It as var

Declare a @FetchRequest property as var, since the wrapper updates its stored results as the data changes.

Quick Check

You wired up @FetchRequest. A quick check on how it behaves.

Recap

You used @FetchRequest to pull records into a view, sort and filter them, and let the list refresh itself as data changes. ✨

常见问题解答

「使用 @FetchRequest 获取数据」课时是免费的吗？

是的 — 「使用 @FetchRequest 获取数据」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。

「使用 @FetchRequest 获取数据」这节课中我会学到什么？

将托管对象直接加载到视图中。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 2 节课，共 4 节。

「使用 @FetchRequest 获取数据」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。

此课程中的所有课时

← 返回 SwiftUI Academy