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single 与 factory 作用域

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single 与 factory 作用域 是 CoddyKit 上的免费 Kotlin Multiplatform 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 Kotlin Multiplatform Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Kotlin Multiplatform 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。

Two Ways to Build

Koin gives you two main definition keywords: single and factory. They differ in one thing, how often Koin builds the object.

single Means One Instance

A single is created once and shared everywhere. Every part of your app that asks for it receives the very same object. 🔁

single { UserRepository(get()) }

factory Means Fresh Each Time

A factory builds a brand new instance on every request. Nothing is cached, so two callers never share the same object.

factory { ProfileUseCase(get()) }

When to Pick single

Use single for things that hold state or are expensive to build, like a repository, an HTTP client, or a database driver.

When to Pick factory

Reach for factory when each caller wants its own short-lived object, such as a stateless use case or a one-shot mapper.

single Is Lazy by Default

A single is not built when you declare it. Koin creates it the first time something actually asks for it, then keeps it around.

Force Eager Creation

Need a single ready at startup instead of on first use? Add createdAtStart so Koin builds it the moment the container starts.

single(createdAtStart = true) { Analytics() }

Mixing Them in a Graph

A single repository can depend on a factory mapper. Koin happily mixes scopes, building the factory fresh inside the long-lived single.

Watch Out for Shared State

If you make something single by mistake, callers may share state you meant to keep private, a classic source of subtle multiplatform bugs.

A Practical Module

Here a long-lived repository and a fresh use case live side by side, each scoped to match how it is used.

module {
    single { UserRepository(get()) }
    factory { LoginUseCase(get()) }
}

Default to single

When unsure, start with single. Most app-wide services want one instance, and you can switch to factory the moment you truly need fresh objects.

Quick Check

Pick the right scope behavior.

在交互式课程中回答

Recap

You learned that single shares one instance while factory builds a new one each time. Pick single for shared services, factory for short-lived helpers. 👍

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常见问题解答

「single 与 factory 作用域」课时是免费的吗？

是的 — 「single 与 factory 作用域」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 Kotlin Multiplatform Academy 课程的其余内容，请升级到 CoddyKit PRO。 Kotlin Multiplatform Academy 课程共包含 4 节课。

「single 与 factory 作用域」这节课中我会学到什么？

选择单例还是全新实例你通过在浏览器中直接运行的动手代码来练习 Kotlin Multiplatform 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 Kotlin Multiplatform Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Kotlin Multiplatform 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。

「single 与 factory 作用域」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 Kotlin Multiplatform Academy 课中编写并运行代码吗？

能。每节 Kotlin Multiplatform 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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