flutter firestore, add new object in array

Right Format is :

Firestore.instance.collection(city).document('Attractions').updateData({"data": FieldValue.arrayUnion(obj)});

updateData Take Map<String,dynamic> as data.

In your Code you are having , as separator between key - value instead it should be :

@anmol.majhail 's is right, but to solve @Sami Ullah's problem, you must first make a list and add the object into the list like this:

var list = [objectBeingAdded];
Firestore.instance.collection('city').document('Attractions').updateData({"data": FieldValue.arrayUnion(list)});