如何使用模板文字型別從介面獲取特定鍵？

我有以下代碼接受possibleColumns給定資料庫表的字串陣列。然后它使用傳入source并嘗試將其與包含{source}_id.

例如，possibleColumns可以包含["id", "name", "duedil_id", "salesforce_id"]和來源duedil，然后檢查任何被呼叫的列duedil_id并回傳它。

邏輯很好，但回傳的型別不正確，目前它只回傳可能的值作為該型別中的任何列，但我想使用模板文字型別只回傳包含<value>_id. 正如評論中所見，我正在嘗試使用該Extract型別但沒有運氣。

/**
 * Takes a list of columns for a specific table and a source and checks for any columns that
 * match `${source}_id`.
 * @template T The desired output type
 * @param possibleColumns string array of columns of type T
 * @param source The source to convert in question
 * @returns a key of one of the columns of T or undefined if not matched
 */
export function getProviderIdColumn<T>(possibleColumns: (keyof T)[], source: string) {
    // Attempt to extract only keys that contain _id at the end
    // as Extract<keyof T extends `${infer _}_id` ? keyof T : never, T>
    const providerIdColumn = `${source}_id` as keyof T;
    if (possibleColumns.includes(providerIdColumn)) {
        return providerIdColumn;
    }

電流輸出

"id" | "name" | "duedil_id" | "salesforce_id"

期望的輸出

"duedil_id" | "salesforce_id"

我對打字稿的了解不是很好，所以請忽略任何濫用的術語。

最小的作業示例

export interface Model {
    id: number,
    name: string | null,
    boardex_id: string | null,
    source: string,
    duedil_id: string | null,
    zoom_info_id: string | null,
}

/**
 * Takes a list of columns for a specific table and a source and checks for any columns that
 * match `${source}_id`.
 * @template T The desired output type
 * @param possibleColumns string array of columns of type T
 * @param source The source to convert in question
 * @returns a key of one of the columns of T or undefined if not matched
 */
export function getProviderIdColumn<T>(possibleColumns: (keyof T)[], source: string) {
    // Attempt to extract only keys that contain _id at the end
    // as Extract<keyof T extends `${infer _}_id` ? keyof T : never, T>
    const providerIdColumn = `${source}_id` as keyof T;
    if (possibleColumns.includes(providerIdColumn)) {
        return providerIdColumn;
    }
    return undefined;

}

// A function here returns a string array of the keys in Model.
const columnInfo: (keyof Model)[] = ["id", "name", "boardex_id", "source", "duedil_id", "zoom_info_id"];

const source = "boardex";

// Returned values here are fine but I want to get the desired output.
const providerIdColumn = getProviderIdColumn<Model>(columnInfo, source);

游樂場鏈接

uj5u.com熱心網友回復：

我們可以通過使用這個映射型別來提取_id屬性名稱來做到這一點：

/**
 * Gets a union of the literal types in `T` that end with `_id`.
 */
type IdKeys<T extends any[]> = keyof {
    [Key in T[number] as Key extends `${string}_id` ? Key : never]: null;
};

然后在函式中使用它：

/**
 * Takes a list of columns for a specific table and a source and checks for any columns that
 * match `${source}_id`.
 * @template ObjectType The desired output type
 * @param possibleColumns string array of columns of type T
 * @param source The source to convert in question
 * @returns a key of one of the columns of T or undefined if not matched
 */
export function getProviderIdColumn<ObjectType>(
    possibleColumns: (keyof ObjectType)[],
    source: string
): IdKeys<(keyof ObjectType)[]> | undefined {
    // Sadly, we have to have a type assertion, since `source` is type `string`
    const providerIdColumn = `${source}_id` as IdKeys<(keyof ObjectType)[]>;
    if (possibleColumns.includes(providerIdColumn)) {
        return providerIdColumn;
    }
    return undefined;
}

結果是在您的示例呼叫中：

const providerIdColumn = getProviderIdColumn<Model>(columnInfo, source);

...providerIdColumn的型別是"boardex_id" | "duedil_id" | "zoom_info_id" | undefined.

游樂場示例

標籤：打字稿

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