在循环中调用 conn.query 导致：变量 'conn' 隐式具有 'any' 类型

Question

我有一条如下所示的路线，我想在其中从数据库中获取所有 posts（如在 Twitter 中）。我已将每个 post 的喜欢和图像分开在其自己的 sql table 中，称为“post_likes”和“post_images”。

检索 post 后，我想为每个 post 添加喜欢，然后将其发送回客户端。

但是遍历数组并每次调用 conn.query 都会给我这两个错误：

error TS7034: Variable 'conn' implicitly has type 'any' in some locations where its type cannot be determined.

error TS7005: Variable 'conn' implicitly has an 'any' type.

为什么 typescript 无法确定 map 或 forEach 循环中 conn 的类型？

router.get("/get/:token", async (req: Request, res: Response) => {
  /**
   * Gets all Post from you and your friends
   */

  ... 

  let conn;  // ERROR <-- Variable 'conn' implicitly has type 'any' in some locations where its type cannot be determined.
  
  try {
    conn = await pool.getConnection();

    ... 

    /* get all posts */
    const queryGetPostsResult = await conn.query(queryGetPosts);
    const getPosts: Array<Post> = [...queryGetPostsResult];

    /* add images and likes to each post */
    let clientPosts: Array<ClientPost> = await Promise.all(getPosts.map(async (post: Post) => {

      /* FIXME get the likes */
      const queryGetLikes: string = `SELECT user_id FROM post_likes WHERE post_id=?`

      const queryGetLikesResult = await conn.query(queryGetLikes, [post.id]); // ERROR <-- Variable 'conn' implicitly has an 'any' type.

      const likes: Array<number> = queryGetLikesResult.map((x: { user_id: number }) => x.user_id);

      /* TODO get the images */
      const images: Array<string> = [];


      const clientPost: ClientPost = {
        id: post.id,
        writtenBy: post.written_by,
        content: post.content,
        writtenAt: post.written_at,
        images,
        likes,
      };

      return clientPost;
    }));

    return res.send(clientPosts);
  } catch(err: unknown) {
    throw console.log(colors.red(`/api/post/get/:token => ${err}`));
  } finally {
    if (conn) return conn.release();
  }
});

Answer 1

喜欢T.J。 Crowder 建议问题是 let conn; 处缺少类型注释，但我仍然不明白为什么打字稿只在我尝试在循环内调用 conn.query() 时抛出错误。如果有人知道请给我解释一下。

我还必须添加 if (!conn) throw "conn is undefined" 以跳出 try & map 块。

所以我将路线编辑为以下内容：

router.get("/get/:token", async (req: Request, res: Response) => {
  /**
   * Gets all Post from you and your friends
   */

  ... 

  let conn: PoolConnection | undefined;  // <-- ADDED TO FIX THE ERROR!!!
  
  try {
    conn = await pool.getConnection();
    if (!conn) throw "conn is unknown"; // <-- ADDED TO FIX THE ERROR!!!

    ... 

    /* get all posts */
    const queryGetPostsResult = await conn.query(queryGetPosts);
    const getPosts: Array<Post> = [...queryGetPostsResult];

    /* add images and likes to each post */
    let clientPosts: Array<ClientPost> = await Promise.all(getPosts.map(async (post: Post) => {

      if (!conn) throw "conn is unknown"; // <-- ADDED TO FIX THE ERROR!!!

      /* FIXME get the likes */
      const queryGetLikes: string = `SELECT user_id FROM post_likes WHERE post_id=?`

      const queryGetLikesResult = await conn.query(queryGetLikes, [post.id]);

      const likes: Array<number> = queryGetLikesResult.map((x: { user_id: number }) => x.user_id);

      /* TODO get the images */
      const images: Array<string> = [];


      const clientPost: ClientPost = {
        id: post.id,
        writtenBy: post.written_by,
        content: post.content,
        writtenAt: post.written_at,
        images,
        likes,
      };

      return clientPost;
    }));

    return res.send(clientPosts);
  } catch(err: unknown) {
    throw console.log(colors.red(`/api/post/get/:token => ${err}`));
  } finally {
    if (conn) return conn.release();
  }
});

在循环中调用 conn.query 导致：变量 'conn' 隐式具有 'any' 类型

Calling conn.query in a loop causes: Variable 'conn' implicitly has an 'any' type

javascript

mariadb

express

typescript