Question

使用mysql2 / promise库，我的一个对象部分包含以前SELECT语句中未解析的promise。

插入时，我收到错误的整数值错误消息，因为承诺尚未解决。什么是解决所包含的承诺的优雅方式？

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;
    });
}

没有async/await你可以这样做：

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;
    });
});

在MySQL INSERT之前解析promise对象

1 个答案: