在MySQL之前解析承諾對象INSERT

Question

使用mysql2/promise庫時，我的一個對象部分包含來自先前SELECT語句的未解決的承諾。

插入時，我得到一個不正確的整數值錯誤消息，因爲承諾尚未解決。什麼是解決包含的承諾的優雅方式？

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; 
    }); 
} 

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; 
    }); 
});