CODEWITHSUNDEEP
firebaseflutterdartgoogle-cloud-firestore
Damandroid
Damandroid

Reputation: 974

How to use Stream callbacks in Cloud Firestore

I have a few questions (I am new to Dart) w.r.t the code below which I found. What I am trying to achieve: 1) Write more than one line in the brackets for errors. But I get error saying 'set literals were supported upto 2.2....'. It would also be good to know the list of possible errors so I can alert the user accordingly.

2) Increment a counter pertaining to number of documents and keep storing document id's in one variable, by overwriting the last value if more than one document is found. I am trying to check that there should only be one document and take action if counter goes to 2.

void _checkIfAdmin() {
Firestore.instance
    .collection('Admin')
    .where('Email', isEqualTo: widget._user.email)
    .snapshots()
    .handleError((error)=>{
      //
      })
    .listen((data) => data.documents.forEach((doc) => gpCounter+=1)); // Store document id?
print('Counter: $gpCounter');

}

Here I am getting printed gpCounter=0 when I know there are two documents in there. I tried adding async/await in the function but it seems the firebase statement does not return any future so I get a warning to use await only for futures.

Upvotes: 1

Views: 624

Answers (1)

creativecreatorormaybenot
creativecreatorormaybenot

Reputation: 126574

I will try to address as many issues as I could understand in your question. If you have any other issues, you should probably ask another question.

  1. Set literals: the syntax for anonymous functions is () {} and not () => {}.
    () => is a shorthand syntax to return the value of a single expressions and in your case, you are returning a Set in your anonymous functions because {} create Set's (or Map's if you have colons in there).
    The solution for this is (error) { ... }.

  2. You print your gpCounter value synchronously, however, you are listening to a Stream.
    Because of that, you should move your print statement to your listen function:

    .listen(data) {
        print('Counter: ${data.documents.length}');
      })

Upvotes: 1

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