How to delete duplicates of a List<MyDataModel> (Dart/Flutter) - list

Question

I have a futurebuilder that builds the UI based on a List, it does the job, however I get duplicates due to the UI being built again and again whenever I navigate. My question is, is there a innate method in Dart that can remove duplicates from a list? I've tried this StackOverflow question however it doesn't work.
Here is my custom model:
class HomeList {
Widget navigateScreen;
String imagePath;
PatientInfo patientInfo;
HomeList({
this.navigateScreen,
this.imagePath = '',
this.patientInfo,
});
static List<HomeList> homeList = [];
}
Here is my function for the futureBuilder i'm getting the data from my cloud_firestore:
_getPatients() async {
if (didLoadpatients == 0) {
print('this is didloadpatients at start of func $didLoadpatients');
var document = await db
.collection('users')
.document(mUser.uid)
.collection('patients');
document.getDocuments().then((QuerySnapshot query) async {
query.documents.forEach((f) {
uids.add(f.data['uID']);
});
didLoadpatients++;
print('this is didloadpatients at end of func $didLoadpatients');
for (var i = 0; i < uids.length; i++) {
var userDocuments = await db.collection('users').document(uids[i]);
userDocuments.get().then((DocumentSnapshot doc) {
print(doc.data);
homeList.add(HomeList(
imagePath: 'assets/fitness_app/fitness_app.png',
patientInfo: new PatientInfo.fromFbase(doc.data)));
});
print(homeList);
}
});
} else
print('I am leaving the get patient function');
}
Future<bool> getData() async {
_getCurrentUser();
await Future.delayed(const Duration(milliseconds: 1500), () async {
_getPatients();
});
return true;
}
Any help would be appreciated thank you!

Answer 1

To remove duplicates you can use Set Data Structure instead of List.
Just use Set instead of List to get unique values only.

Answer 2

Before Adding you can Remove Element from model this will Work
dummymodel.removeWhere((m) => m.id == id);
dummymodel.add(dummymodel.fromJson(data));

Answer 3

To Remove Duplicates from Data Model simply use Set (Data structure),
Original List with Duplicate Entries:
List<MyDataModel> mList = [MyDataModel(1), MyDataModel(2), MyDataModel(1), MyDataModel(3)];
New List that removes duplicate Entries from your List<MyDataModel>:
List<MyDataModel> mNewList = list.toSet().toList();
Output:
The result will be like
MyDataModel(1), MyDataModel(2), MyDataModel(3)

Answer 4

To remove the duplicate elements from custom object list, you need to override == and hashcode methods in your POJO class and then add the items in Set and again convert set to list to remove duplicate objects. Below is the working code:-
class TrackPointList {
double latitude;
double longitude;
String eventName;
Time timeZone;
TrackPointList({
this.latitude,
this.longitude,
this.eventName,
this.timeZone,
});
#override
bool operator==(other) {
// Dart ensures that operator== isn't called with null
// if(other == null) {
// return false;
// }
if(other is! TrackPointList) {
return false;
}
// ignore: test_types_in_equals
return eventName == (other as TrackPointList).eventName;
}
int _hashCode;
#override
int get hashCode {
if(_hashCode == null) {
_hashCode = eventName.hashCode;
}
return _hashCode;
}
factory TrackPointList.fromJson(Map<String, dynamic> json) => TrackPointList(
latitude: json["latitude"].toDouble(),
longitude: json["longitude"].toDouble(),
eventName: json["eventName"],
timeZone: timeValues.map[json["timeZone"]],
);
Map<String, dynamic> toJson() => {
"latitude": latitude,
"longitude": longitude,
"eventName": eventName,
"timeZone": timeValues.reverse[timeZone],
};
}
Above is the POJO class. Now below is the method which helps you to filter the objects according to the eventName data member.
List<TrackPointList> getFilteredList(List<TrackPointList> list){
final existing = Set<TrackPointList>();
final unique = list
.where((trackingPoint) => existing.add(trackingPoint))
.toList();
return unique;
}
This will work definitely.
Please +1 if it helps you.

Answer 5

I've come up with quite a brute force solution. Instead of
_getPatients() async {
if (didLoadpatients == 0) {
print('this is didloadpatients at start of func $didLoadpatients');
var document = await db
.collection('users')
.document(mUser.uid)
.collection('patients');
document.getDocuments().then((QuerySnapshot query) async {
query.documents.forEach((f) {
uids.add(f.data['uID']);
});
didLoadpatients++;
print('this is didloadpatients at end of func $didLoadpatients');
for (var i = 0; i < uids.length; i++) {
var userDocuments = await db.collection('users').document(uids[i]);
userDocuments.get().then((DocumentSnapshot doc) {
print(doc.data);
homeList.add(HomeList(
imagePath: 'assets/fitness_app/fitness_app.png',
patientInfo: new PatientInfo.fromFbase(doc.data)));
});
print(homeList);
}
});
} else
print('I am leaving the get patient function');
}
I've done what #Jay Mungara says and clear my Set everytime my UI rebuilds:
_getPatients() async {
homeList.clear();
if (didLoadpatients == 0) {
print('this is didloadpatients at start of func $didLoadpatients');
var document = await db
.collection('users')
.document(mUser.uid)
.collection('patients');
document.getDocuments().then((QuerySnapshot query) async {
query.documents.forEach((f) {
uids.add(f.data['uID']);
});
didLoadpatients++;
print('this is didloadpatients at end of func $didLoadpatients');
for (var i = 0; i < uids.length; i++) {
var userDocuments = await db.collection('users').document(uids[i]);
userDocuments.get().then((DocumentSnapshot doc) {
print(doc.data);
homeList.add(HomeList(
imagePath: 'assets/fitness_app/fitness_app.png',
patientInfo: new PatientInfo.fromFbase(doc.data)));
});
print(homeList);
}
});
} else
print('I am leaving the get patient function');
}
Thank you for all your answers!

Answer 6

this is a small examples to remove duplicate element
removeDuplicate() {
List<dynamic> demoList = [
{"userId": 1, "id": 1, "name": "thappu1"},
{"userId": 2, "id": 2, "name": "appu"},
{"userId": 1, "id": 1, "name": "thappu1"},
{"userId": 2, "id": 2, "name": "appu"},
{"userId": 2, "id": 2, "name": "appu"},
{"userId": 2, "id": 2, "name": "appu"},
{"userId": 2, "id": 2, "name": "appu"},
];
var toRemove = {};
demoList.forEach((e) {
toRemove.putIfAbsent("$e", () => e);
});
print(toRemove.keys.toList());
}
output is
[{userId: 1, id: 1, name: thappu1}, {userId: 2, id: 2, name: appu}]