Javascript 使用实时更新时如何检查云 Firestore 文档是否存在
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How to check if a cloud firestore document exists when using realtime updates
提问by Stewart Ellis
This works:
这有效：
db.collection('users').doc('id').get()
.then((docSnapshot) => {
if (docSnapshot.exists) {
db.collection('users').doc('id')
.onSnapshot((doc) => {
// do stuff with the data
});
}
});
... but it seems verbose. I tried doc.exists, but that didn't work. I just want to check if the document exists, before subscribing to realtime updates on it. That initial get seems like a wasted call to the db.
......但似乎很冗长。我试过了doc.exists，但这没有用。我只想在订阅文档的实时更新之前检查文档是否存在。最初的 get 似乎是对数据库的浪费调用。
Is there a better way?
有没有更好的办法？
回答by Excellence Ilesanmi
Your initial approach is right, but it may be less verbose to assign the document reference to a variable like so:
您最初的方法是正确的，但将文档引用分配给像这样的变量可能不那么冗长：
const usersRef = db.collection('users').doc('id')
usersRef.get()
.then((docSnapshot) => {
if (docSnapshot.exists) {
usersRef.onSnapshot((doc) => {
// do stuff with the data
});
} else {
usersRef.set({...}) // create the document
}
});
Reference: Get a document
参考：获取文档
