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定义 @Model 类型

将类标注为持久化模型。

定义 @Model 类型 是 CoddyKit 上的免费 SwiftUI Academy 课时。这是第 1 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。

Meet SwiftData

SwiftData is Apple's modern way to save app data right on the device. You describe your data once, and it handles storage for you. 💾

The @Model Macro

You turn a plain class into a saved type by adding the @Model macro above it. That one line makes every instance persistable.

@Model
class Task {
}

Stored Properties

Every stored property on a @Model class is saved automatically. No extra annotations are needed for basic values like text or numbers.

@Model
class Task {
    var title: String
    var isDone: Bool
}

Models Are Classes

SwiftData models must be classes, not structs. SwiftData tracks them by reference so it can watch changes and save them.

Adding an Initializer

Give your model an init so you can create instances with starting values. This keeps your stored properties set when a task is made.

init(title: String, isDone: Bool = false) {
    self.title = title
    self.isDone = isDone
}

Supported Property Types

SwiftData saves common types out of the box: String, Int, Double, Bool, Date, and Data all just work without setup.

var due: Date
var priority: Int

Optional Properties

Mark a value optional when it may be missing. SwiftData stores nil happily, which is great for fields the user has not filled in yet.

var note: String?

Unique Constraints

Add @Attribute(.unique) to stop duplicate values for a property. SwiftData will keep that field one-of-a-kind across your store.

@Attribute(.unique) var id: UUID

Relationships Between Models

Models can point to each other with a @Relationship. This links one record to another, like a project owning many tasks.

@Relationship var tasks: [Task]

Cascade Deletes

A .cascade delete rule removes related records together. Delete a project and its tasks vanish too, keeping your data tidy.

@Relationship(deleteRule: .cascade)
var tasks: [Task]

Ignoring a Property

Use @Transient for values you do not want saved, like a temporary cache. SwiftData skips these when writing to disk.

@Transient var isEditing = false

Quick Check

Quick check on defining models.

Recap: Defining Models

You learned that @Model turns a class into saved data, with normal properties, optionals, unique attributes, and relationships. Your data shape is ready. 🎉

常见问题解答

「定义 @Model 类型」课时是免费的吗？

是的 — 「定义 @Model 类型」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。

「定义 @Model 类型」这节课中我会学到什么？

将类标注为持久化模型。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 1 节课，共 4 节。

「定义 @Model 类型」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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