I have array of objects, I want to add new object when user enter new data in the array?
Firestore.instance.collection(city).document('Attractions').updateData( "data", FieldValue.arrayUnion(obj) ); This shows error, How can I achieve this with flutter?
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)}); 
Say this is the data you want to add
Map<String, dynamic> someData = { 'foo': 1, 'bar': true, }; Add the data with unique auto-generated ID:
var collection = FirebaseFirestore.instance.collection('collection'); collection .add(someData) .then((_) => print('Added')) .catchError((error) => print('Add failed: $error')); Add the data with your own ID:
var collection = FirebaseFirestore.instance.collection('collection'); collection .doc('document_id') // <-- Document ID .set(someData) .then((_) => print('Added')) .catchError((error) => print('Add failed: $error')); Add the object to an array:
var collection = FirebaseFirestore.instance.collection('collection'); collection .doc('document_id') // <-- Document ID .set({'data': FieldValue.arrayUnion(list)}) // <-- Add data .then((_) => print('Added')) .catchError((error) => print('Add failed: $error')); 
final washingtonRef = db.collection("cities").doc("DC"); // Atomically add a new region to the "regions" array field. washingtonRef.update({ "regions": FieldValue.arrayUnion(["greater_virginia"]), }); // Atomically remove a region from the "regions" array field. washingtonRef.update({ "regions": FieldValue.arrayRemove(["east_coast"]), }); This is a working function I built that adds new Maps to an array in my Firestore Services class. I'm using Json Serializable to annotate all my model classes. userTemplateSections is a data field in my userTemplate firestore documents. I take userTemplate as a constructor of the 'addUserTemplateSection' function to make sure I'm editing the correct document.
I also added the function I made to delete Maps from a firestore document array.
'''
Future<void> addUserTemplateSection( {UserTemplate userTemplate, String title, String summary}) async { try { final UserTemplateSection userTemplateSection = UserTemplateSection(title: title, summary: summary); await _firestore .document(FirestorePath.userTemplate(uid, userTemplate.id)) .updateData( { 'userTemplateSections': FieldValue.arrayUnion([userTemplateSection.toJson()]) }, ); } catch (e) { print(e); } } '''
'''
Future<void> deleteUserTemplateSection({ UserTemplate userTemplate, UserTemplateSection userTemplateSection, }) async { try { await _firestore .document(FirestorePath.userTemplate(uid, userTemplate.id)) .updateData( { 'userTemplateSections': FieldValue.arrayRemove([userTemplateSection.toJson()]) }, ); } catch (e) { print(e); } } '''
