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将 DTO 映射为领域模型

分离网络数据结构和领域类型

将 DTO 映射为领域模型 是 CoddyKit 上的免费 Kotlin Multiplatform 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 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 Kinds of Models

Your app actually has two shapes of data: the raw DTO from the API and the clean domain model your code wants.

What a DTO Is

A DTO, or data transfer object, mirrors the JSON exactly, even when the field names are messy or awkward.

@Serializable
data class UserDto(val user_name: String, val avatar_url: String?)

Why Not Use DTOs Directly

If your whole app uses DTOs, a tiny API change ripples everywhere. A domain model protects you from that.

The Domain Model

The domain model is shaped for your code: nice names, no nullable junk, exactly the fields the UI needs.

data class User(val name: String, val avatar: String)

Map in One Function

Write a small mapping function that turns a DTO into a domain model, all in one tidy, testable place.

fun UserDto.toDomain() = User(name = user_name, avatar = avatar_url ?: "")

Handle Nulls While Mapping

Mapping is the perfect spot to apply defaults, so missing or null JSON fields never crash the rest of the app.

Map Lists Too

For a list response, call map on the collection to convert every DTO into a domain item at once.

fun List<UserDto>.toDomain() = map { it.toDomain() }

Do It in the Repository

The repository fetches DTOs, then maps them to domain models, so callers only ever see the clean type.

override suspend fun getUsers() =
    client.get(url).body<List<UserDto>>().toDomain()

DTOs Stay Internal

Keep DTO classes internal to the data layer. Nothing outside the repository should ever import them.

Decoupled and Safe

Now the API can rename a field and you fix just the mapper, while the domain model and UI stay calm.

The Mapping Layer

This is the boundary in action: a DTO comes in, the mapper runs, and a clean domain model comes out.

val dto: UserDto = client.get(url).body()
val user: User = dto.toDomain()

Quick Check

Why map DTOs to separate domain models?

Recap

DTOs mirror raw JSON and stay in the data layer, while a mapping function turns them into clean domain models the rest of the app uses.

常见问题解答

「将 DTO 映射为领域模型」课时是免费的吗？

是的 — 「将 DTO 映射为领域模型」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 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。

「将 DTO 映射为领域模型」这节课中我会学到什么？

分离网络数据结构和领域类型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 3 节课，共 4 节。

「将 DTO 映射为领域模型」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 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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