强制类型是接口的子类型并扩展编号

Question

我正在使用这些接口

/**
 * Interface for entities
 */
export interface Entity extends Object {
    readonly id: EntityId;
}

/**
 * Interface for collection-based state
 */
export interface Collection<T extends Entity> extends Object {
    readonly entities: { [key: string]: T };
    readonly ids: EntityId[];
}

我正在编写一个辅助函数，它给定路径，增加集合中实体的相应值。

例子：

Collection.increment(myCollection, 'some-id', ['stats', 'total']);

这些是我目前的类型

    export function increment<
        C extends Collection<any>,
        E = C extends Collection<infer U> ? U : never,
        K1 extends keyof E = keyof E,
        V1 extends E[K1]= E[K1]
        >(collection: C, entityId: string, path: K1 | [K1]): C
    export function increment<
        C extends Collection<any>,
        E = C extends Collection<infer U> ? U : never,
        K1 extends keyof E = keyof E,
        V1 = Exclude<E[K1], void>,
        K2 extends keyof V1 = keyof V1,
        V2 extends V1[K2]= V1[K2]
        >(collection: C, entityId: string, path: K1 | [K1] | [K1, K2]): C

对于这个例子，打字非常冗长，因为它们被用来检查传入的类型

上述类型有效，唯一的问题是非数字类型的路径仍然有效。

I tried something like the below to force it to only allow numbers

export function increment<
    C extends Collection<any>,
    E = C extends Collection<infer U> ? U : never,
    K1 extends keyof E = keyof E,
    V1 extends E[K1]= E[K1]
    >(collection: C, entityId: string, path: K1 | [K1]): C
export function increment<
    C extends Collection<any>,
    E = C extends Collection<infer U> ? U : never,
    K1 extends keyof E = keyof E,
    V1 = Extract<Exclude<E[K1], void>, number>, // Note the Extract
    K2 extends keyof V1 = keyof V1,
    V2 extends V1[K2]= V1[K2]
    >(collection: C, entityId: string, path: K1 | [K1] | [K1, K2]): C

但上述并没有按预期强制执行约束

有什么想法吗？

Answer 1

您需要按属性类型过滤可用键。从Omit 类型中获取提示，我们可以使用条件类型来创建一个类型，该类型将根据属性类型过滤掉属性。

type FilterKeysByType<T, U> = ({[P in keyof T]: T[P] extends U ? P: never } & { [x: string]: never })[keyof T];  
// If there is a single key, it must be a key of a number field
export function increment<
    C extends Collection<any>,
    E = C extends Collection<infer U> ? U : never,
    K1 extends FilterKeysByType<E, number | undefined> = FilterKeysByType<E, number | undefined>,
    V1 extends Exclude<E[K1], void> = Exclude<E[K1], void>
>(collection: C, entityId: string, path: K1 | [K1]): C
// If there are two keys, the first key, can be any  type, but the second key must be the key of a number field 
export function increment<
    C extends Collection<any>,
    E = C extends Collection<infer U> ? U : never,
    K1 extends keyof E = keyof E,
    V1 = Exclude<E[K1], void>,
    K2 extends FilterKeysByType<V1, number| undefined> = FilterKeysByType<V1, number| undefined>,
    V2 extends V1[K2]= V1[K2]
    >(collection: C, entityId: string, path: [K1, K2]): C

// Usage
declare var c : Collection<Comment>;

interface Comment extends Entity{
    name: string;
    value: number;
    optValue?: number;
    subcomment: Comment;
    optSubcomment?: Comment;
}

increment(c, "", "value"); //ok
increment(c, "", "optValue"); //ok
increment(c, "", "name");// error
increment(c, "", ["subcomment", "value"]); // ok
increment(c, "", ["subcomment", "optValue"]); // ok
increment(c, "", ["subcomment", "name"]); // error
increment(c, "", ["optSubcomment", "value"]); // ok
increment(c, "", ["optSubcomment", "optValue"]); // ok
increment(c, "", ["optSubcomment", "name"]); // error

Answer 2

我尽量不打破条件类型，除非没有它们我无法解决问题（因为它们有时具有令人毛骨悚然的推理属性，我无法绕开我的大脑）。那么这些类型呢？

declare function increment<
 C extends Collection<Entity & Record<K1,Record<K2,number>>>, 
 K1 extends string, 
 K2 extends string>(collection: C, entityId: string, path: [K1, K2]): C;
declare function increment<
 C extends Collection<Entity & Record<K1, number>>, 
 K1 extends string>(collection: C, entityId: string, path: K1 | [K1]): C;

只有C 和K1（可能还有K2）。这个想法是C 应该是Collection<Entity & Something>，其中Something 是Record<K1, number> 或Record<K1, Record<K2, number>>，这取决于path 中有多少元素。 （以防万一，Record<K extends string, V> 定义为 {[P in K]: V}，它仅表示“具有 K 类型的键和 V 类型的值的对象”。）

您可以验证它的行为是否符合要求：

interface Ent extends Entity {
  stats: {
    total: number,
    color: string
  }
  height: number,
  name: string
}

declare const myCollection: Collection<Ent>;

increment(myCollection, 'some-id', ['stats', 'total']); // okay
increment(myCollection, 'some-id', 'height'); // okay
increment(myCollection, 'some-id', ['height']); // okay

increment(myCollection, 'some-id', ['stats']); // error
increment(myCollection, 'some-id', ['stats', 'name']); // error
increment(myCollection, 'some-id', ['name']); // error
increment(myCollection, 'some-id', ['stats', 'color']); // error
increment(myCollection, 'some-id', ['random']); // error

希望有所帮助；祝你好运！