通用递归修改 Typescript 中的给定 type/interface

Question

我正在努力制作一个泛型，它会递归地修改在嵌套的递归数据结构中找到的所有元素。这是我的数据结构的示例。使用此递归数据定义，任何 post 都可以有无限数量的评论和回复。

type Post = {
    user: string,
    content: string,
    comments: Comment[],
    reactions: Reaction[],
}

type Comment = {
    user: string,
    content: string,
    replies: Comment[],
}

type Reaction = {
    user: string,
    reaction: "laugh" | "cry" | "smile",
}

我想要的是一个通用包装器，我可以将其与这些和 任何其他数据类型 一起使用，它将每个 user 字段替换为其他内容。我可以为最高级别执行此操作：

type UserFilled<T> = Omit<"user", T> & { user: { id: string, name: string }}

但这只会更改 Post 的 user 字段。我还希望它向下爬行并为每个评论替换更改 user 字段，如果有更多字段，则用于反应、喜欢或任何其他结构 user他们。

我见过但我无法使用联合将修改后的属性添加回来，我想知道是否有更直接的方法来做到这一点，而不仅仅是省略但也替换该字段？

例如，使用泛型我希望能够做到这一点：

const post: Post = {
    user: "1234",
    content: "this is a post",
    comments: [{
        user: "3456",
        content: "I agree",
        replies: [{
            user: "1234",
            content: "thanks",
        }],
    }],
    reactions: [{
        user: "5678",
        reaction: "smile",
    }],
};

const postWUserInfo: UserFilled<Post> = {
    user: { id: "1234", name: "Bob" },
    content: "this is a post",
    comments: [{
        user: { id: "3456", name: "Jim" },
        content: "I agree",
        replies: [{
            user: { id: "1234", name: "Bob" },
            content: "thanks",
        }],
    }],
    reactions: [{
        user: { id: "5678", name: "Jim" },
        reaction: "smile",
    }],
};

Answer 1

您可以创建一个可以递归检查和替换密钥的 DeepReplace 实用程序。另外我强烈建议只替换值并确保密钥保持不变。

// "not object"
type Primitive = string | Function | number | boolean | Symbol | undefined | null 

// If T has key K ("user"), replace it
type ReplaceKey<T, K extends string, R> = T extends Record<K, unknown> ? Omit<T, K> & Record<K, R> : T

// Check and replace object values
type DeepReplaceHelper<T, K extends string, R, ReplacedT = ReplaceKey<T, K, R>> = {
    [Key in keyof ReplacedT]: ReplacedT[Key] extends Primitive ? ReplacedT[Key] : ReplacedT[Key] extends unknown[] ? DeepReplace<ReplacedT[Key][number], K, R>[] : DeepReplace<ReplacedT[Key], K, R>
}

// T = object, K = key to replace, R = replacement value
type DeepReplace<T, K extends string, R> = T extends Primitive ? T : DeepReplaceHelper<T, K, R>

// Define new type for "user" key
interface UserReplacement {
    id: string
    name: string
}


type UserFilled<T> = DeepReplace<T, "user", UserReplacement>

Typescript Playground with step by step explanation

通用递归修改 Typescript 中的给定 type/interface

Generic to recursively modify a given type/interface in Typescript

typescript

typescript-generics

typescript2.0