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Identifiable 与稳定 ID

使模型遵循 Identifiable，以便正确进行差异比较。

Identifiable 与稳定 ID 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。

The Diffing Problem

When data changes, SwiftUI must know which rows moved, stayed, or vanished. Stable identity makes that diffing correct. 🧩

Why id: .self Is Fragile

Using id: .self breaks when two items are equal or a value changes, because the identity shifts unexpectedly.

Meet Identifiable

The Identifiable protocol asks a type for just one thing: a stable, unique id property that never changes for that item.

protocol Identifiable {
    var id: ID { get }
}

Conforming a Model

Add an id property and conform to Identifiable, and your struct is ready for clean, reliable lists.

struct Task: Identifiable {
    let id = UUID()
    var title: String
}

UUID for Fresh IDs

A UUID generates a guaranteed-unique value, perfect when items have no natural identifier of their own.

let id = UUID()

ForEach Without id:

Once a type is Identifiable, ForEach finds the id by itself, so you can drop the id parameter entirely.

ForEach(tasks) { task in
    Text(task.title)
}

Stable Means Persistent

A good id never changes for the same logical item, even when its title or other fields are edited later on.

Natural Keys

If your data already has a unique field, like a database id, use it instead of generating a new one.

struct User: Identifiable {
    let id: Int
    var name: String
}

Why It Matters for Animation

Correct identity lets SwiftUI animate moves and deletes smoothly instead of redrawing everything.

Avoid Index as ID

Using array indexes as ids is risky: inserting or deleting shifts every index and confuses diffing.

Identity Is About Sameness

Two items with the same id are treated as the same row; different ids mean different rows. Choose ids carefully.

Quick Check

Pick the most reliable approach to row identity.

Recap

You learned Identifiable: a stable id per item lets SwiftUI diff and animate lists correctly, far safer than id: .self. 🎉

常见问题解答

「Identifiable 与稳定 ID」课时是免费的吗？

是的 — 「Identifiable 与稳定 ID」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。

「Identifiable 与稳定 ID」这节课中我会学到什么？

使模型遵循 Identifiable，以便正确进行差异比较。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。

「Identifiable 与稳定 ID」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。

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