在 MySQL INSERT 之前解析 promise 對象

Question

使用 mysql2/promise 庫，我的一個對象部分包含來自先前 SELECT 語句的未解析承諾。

插入時，我收到不正確的整數值錯誤消息，因為承諾尚未解決。 解決包含的承諾的優雅方法是什么？

let insertObj = {
  author: this.authorId // unresolved promise #1
  recipient: this.recipientId // unresolved promise #2
  // ... more promises here
  message: this.messageBody
}

let conn = this.pool.getConnection();
return conn.then((conn) => {
  const res = conn.query("INSERT INTO posts SET ?", [insertObj]);
  conn.release();
  return res
});

Answer 1

使用async/await ：

async function f() {
    // Prefix all promises with await
    let insertObj = {
        author: await this.authorId,
        recipient: await this.recipientId,
        // ... more promises here
        message: await this.messageBody
    }

    let conn = this.pool.getConnection();
    return conn.then((conn) => {
        const res = conn.query("INSERT INTO posts SET ?", [insertObj]);
        conn.release();
        return res;
    });
}

沒有async/await你可以這樣做：

let insertObj = {
    author: this.authorId,
    recipient: this.recipientId,
    // ... more promises here
    message: this.messageBody
};
// Replace promises by their promised values as soon as they resolve:
Object.entries(insertObj).forEach( ([key, value]) => {
    if (typeof Object(value).then === 'function') // it is a "thenable"
        value.then ( response => insertObj[key] = response );
});
// Wait for all of them to resolve
Promise.all(Object.values(insertObj)).then( _ => {
    let conn = this.pool.getConnection();
    return conn.then((conn) => {
        const res = conn.query("INSERT INTO posts SET ?", [insertObj]);
        conn.release();
        return res;
    });
});