Firestore 如何检索过去文档自动生成的 ID？

Question

In Firestore, I have added a single document in a subcollection, I don't know its id because it was added in the past, but I know its path. How to get its id? Should I save its id at the creation?

Thank you

Answer 1

I don't know its id because it was added in the past, but I know its path .

If with "I know its path" you refer to the Document path , then the Document ID is the last element of the path, in which elements are separated by a slash. For example rootCollectionName/parentDocId/parentCollectionName/docId .

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If with "I know its path" you refer to the path of the subcollection , then you could query the subcollection and take the first document, since there is a single doc in the collection.

For example with Dart:

QuerySnapshot querySnapshot = await Firestore.instance.collection("rootCollectionName/parentDocId/parentCollectionName").get();
var documentID = querySnapshot.docs[0].id;