FireStore create a document if not exist

问题

I want to update a doc like this:

db.collection('users').doc(user_id).update({foo:'bar'})

However, if the doc user_id does not exists, the above code will throw an error. Hence, how to tell Firestore to create the student if not exists, in other word, behave like this:

db.collection('users').doc(user_id).set({foo:'bar'})

回答1:

I think you want to use this code:

db.collection('users').doc(user_id).set({foo:'bar'}, {merge: true})

This will set the document with the provided data and will leave other document fields intact. It is best when you're not sure whether the document exists. Simply pass the option to merge the new data with any existing document to avoid overwriting entire documents.

For more detailed about managing data with firestore check this link

回答2:

If you need things like created and updated timestamps, you can use this technique:

let id = "abc123";
let email = "john.doe@gmail.com";
let name = "John Doe";
let document = await firebase.firestore().collection("users").doc(id).get();
if (document && document.exists) {
  await document.ref.update({
    updated: new Date().toISOString()
  });
}
else {
  await document.ref.set({
    id: id,
    name: name,
    email: email,
    created: new Date().toISOString(),
    updated: new Date().toISOString()
  }, { merge: true });
}

This will create the document if it doesn't exist with created and updated timestamps, but only change the updated timestamp if it exists.

来源：https://stackoverflow.com/questions/52277020/firestore-create-a-document-if-not-exist