问题

以下是翻译好的部分：

这是我拥有的用户数据

->firstName
->lastName
->uid
->grade
->friends[<Document Reference UID>] 例如：[users/1, users/2, 等等]

现在我想要获取 uid 为 '1' 的存在的用户列表

String userid="1";
const userRef = admin.firestore().collection('users').doc(userid).get();
var friends = await users
      .where('friends', 'array-contains', userRef)
      .limit(3)
      .get();

->firstName
->lastName
->uid
->grade
->friends[<Document Reference UID>] eg: [users/1, users/2, etc]

String userid="1";
const userRef = admin.firestore().collection('users').doc(userid).get();
var friends = await users
      .where('friends', 'array-contains', userRef)
      .limit(3)
      .get();

答案1

得分: 0

这行代码：

```javascript
const userRef = admin.firestore().collection('users').doc(userid).get();

您的userRef值不是DocumentReference，而实际上是Promise<DocumentSnapshot>。这在后续的.where('friends', 'array-contains', userRef)条件中不会起作用 - 因为不会有任何匹配该类型的文档。

您想要的是：

const userRef = admin.firestore().collection('users').doc(userid);

所以不要在最后加上.get()。现在userRef包含一个DocumentReference，它将匹配具有相同文档引用的文档中的文档。

<details>
<summary>英文:</summary>

This line:

const userRef = admin.firestore().collection('users').doc(userid).get();

Your `userRef` value is not a `DocumentReference`, but is actually a `Promise<DocumentSnapshot>`. And that won't work in the subsequent `.where('friends', 'array-contains', userRef)` condition - as there won't be any documents matching that type.

---

What you want is:

const userRef = admin.firestore().collection('users').doc(userid);

So without `.get()` at the end. Now `userRef` contains a `DocumentReference`, which will match documents that have that same document reference in the `friends` array.

</details>