Firebase instances instead of references

Issue

In the Firebase documentation, it declares final references to Auth or Firestore like this:

CollectionReference users = FirebaseFirestore.instance.collection('items');

My problem is that I have to modify the instance settings on the fly to inject whereBy parameters, specific docs or change the host to emulators etc.

I use new instances repeatedly in my code to serve all these use cases, like this

return FirebaseFirestore.instance
        .collection('contracts')
        .doc(_contractKey)
        .update({'items': _itemArray}).then((value) {
      if (kDebugMode) {
        print("Item updated");
      }
    }).catchError((error) {
      if (kDebugMode) {
        print("Failed to merge data: $error");
      }
      return error;
    });

My question is what the impact is on performance by using new instances in each function instead of referencing a final Firebase reference, set in the constructor? Is it bad practice what I am doing? Do I trigger unnecessary communication between my app and Firebase?

Thanks.

Solution

Firebase SDKs already caches any expensive objects they have to create behind the scenes. While I usually keep a field/variable with collection references for code readability and brevity, performance impact is not a consideration there.

Answered By – Frank van Puffelen

Answer Checked By – Robin (FlutterFixes Admin)