正在獲取 Firebase Firestore 引用

Question

假設我有以下 Firestore 數據結構：

tickets

{
    name: "Testticket",
    open: true,
    users: [
        "users/abcdefg1234" // Firestore reference
    ]
}

收藏users

{
    name: "John Doe",
    color: "green"
}

我的目標是獲取所有open為真的門票，包括用戶 object 而不是參考。

目前我正在這樣做：

// Firebase Functions node.js code

async function getUserData(item) {
  const queryResult = await item.get();
  return await queryResult.data();
}

exports.getOpenTickets = async (request, response) => {
  const query = await db.collection("tickets").where("open", "==", true).get();

  let tickets = [];
  query.forEach(async (doc) => {
    let data = doc.data();
    console.log("data", data);

    data.userObjects = await Promise.all(data.users.map(getUserData));
    console.log("data.userObjects", data.userObjects);

    tickets.push(data);
  });

  return response.json(tickets);
};

問題：用戶數據已獲取，但主 function 並未等待（已通過控制台日志語句進行檢查）。

這是我的 node.js 控制台日志：

i  functions: Beginning execution of "api"
!  Google API requested!
   - URL: "https://oauth2.googleapis.com/token"
   - Be careful, this may be a production service.
>  data {
>    open: true,
>    name: 'Testticket',
>    users: [
>      DocumentReference {
>        _firestore: [Firestore],
>        _path: [ResourcePath],
>        _converter: [Object]
>      }
>    ]
>  }
i  functions: Finished "api" in 1069.554ms
>  data.userObjects [ { color: 'green', name: 'John Doe' } ]

如何解決這個問題？

Answer 1

如果你想在一個循環中運行異步操作，那么你不應該使用forEach 。 嘗試使用for of循環重構代碼，如下所示：

exports.getOpenTickets = async (request, response) => {
  const snap = await db.collection("tickets").where("open", "==", true).get();
  let tickets = [];
  
  for (const doc of snap.docs ) {
    let data = doc.data();
    console.log("data", data);

    data.userObjects = await Promise.all(data.users.map(getUserData));
    console.log("data.userObjects", data.userObjects);

    tickets.push(data);
  }

  return response.json(tickets);
};

另請查看 Using async/await with a forEach loop 。