How to implement group list inside another group list (groupby). Is it possible to use multiple hashcode and operator== in a dart custom object

class People  {
  final String id;
  final String title;
  final String name;
  final String location;
  final String email;
  final String lga;
 

  People({
    @required this.id,
    @required this.title,
    @required this.name,
    @required this.location,
    this.email,
    this.lga,
    
  });


  factory People.fromJson(Map<String, dynamic> json) => People(
    id: json["id"],
    title: json["title"],
    name: json["name"],
    location: json["location"],    
    email: json["email"],
    lga: json["lga"],
   

  );

  Map<String, dynamic> toJson() => {
    "id": id,
    "title": title,
    "name": name,
    "location": location,    
    "email": email,
    "lga": lga,
   
  };


@override
  bool operator ==(o) =>
    o is Priest && townOrigin == o.townOrigin && lga == o.lga;

@override
  int get hashCode => town.hashcode ^ lga.hashcode;

This is possible in a listView between town or lga but my problem is, I want to implement these equals and hashCode in locations too, differently in another ListView.

To make it simple, many people have the same location but I only need one location, from many (as a header) of people from the same location and iterate their names below.

Any help?

[
  {
      "id": "1",
      "name": "Ada Kenneth Kenechukwu",
      "location": "Awka",
      "townOrigin": "Nimo",
      "phone": "080633",
       "lga": "Njikoka",
      
  },
{
      "id": "2",
      "name": "Ugo John",
      "location": "Awka",
      "townOrigin": "Nimo",
      "phone": "08057763",
      "lga": "Njikoka",
     
  },
{
      "id": "3",
      "name": "Okafor Kenneth Kenechukwu",
      "location": "Awka",
      "townOrigin": "Ukpo",
      "phone": "0806363",
      "lga": "Dunukofia",
      
  },
{
      "id": "4",
      "name": "Ndu Agi",
      "location": "Awka",
      "townOrigin": "Ukpo",
      "phone": "0806763",
      "lga": "Dunukofia",
     
  },
 {
      "id": "5",
      "name": "Mma Peter",
      "location": "Awka",
      "townOrigin": "Ichida",
      "phone": "08057763",
       "lga": "Anaocha",
      
  },
{
      "id": "6",
      "name": "Eze Peter",
      "location": "Awka",
      "townOrigin": "Ichida",
      "phone": "0806345",
       "lga": "Anaocha",
     
  }
] 

When you look at this, some have the same location, townOrigin,lga. I have three listView pages in my app where it will display all those(names) from the same location,townOrigin,lga alone respectively . Displaying only names but using one element(like Awka in location) as a subhead.The same applies to all townOrigin, and lga. Looking forward for help.

I have gotten something better, but yet to solve all my issues, with this package sticky_grouped_list, https://pub.dev/packages/sticky_grouped_list

I wanted a group inside a group. I have gotten a group of lga but yet in location inside lga group.

How to merge people from the same location like "Uga" into one.

You could try adding something like this:

extension GroupingBy on Iterable<dynamic> {
  Map<String, List<dynamic>> groupingBy(String key){
    var result = <String, List<dynamic>>{};
    for(var element in this){
      result[element[key]] = (result[element[key]] ?? [])..add(element);
    }
    return result;
  }
}

This will let you group your data elements by a particular field.

First, put your data into a list:

var people = [
      {
        "id": "1",
        "name": "Ada Kenneth Kenechukwu",
        "location": "Awka",
        "townOrigin": "Nimo",
        "phone": "080633",
        "lga": "Njikoka",
      },
      {
        "id": "2",
        "name": "Ugo John",
        "location": "Awka",
        "townOrigin": "Nimo",
        "phone": "08057763",
        "lga": "Njikoka",
      },
      {
        "id": "3",
        "name": "Okafor Kenneth Kenechukwu",
        "location": "Awka",
        "townOrigin": "Ukpo",
        "phone": "0806363",
        "lga": "Dunukofia",
      },
      {
        "id": "4",
        "name": "Ndu Agi",
        "location": "Awka",
        "townOrigin": "Ukpo",
        "phone": "0806763",
        "lga": "Dunukofia",
      },
      {
        "id": "5",
        "name": "Mma Peter",
        "location": "Awka",
        "townOrigin": "Ichida",
        "phone": "08057763",
        "lga": "Anaocha",
      },
      {
        "id": "6",
        "name": "Eze Peter",
        "location": "Awka",
        "townOrigin": "Ichida",
        "phone": "0806345",
        "lga": "Anaocha",
      },
      {
        "id": "7",
        "name": "New Person",
        "location": "Somewhere else",
        "townOrigin": "idk",
        "phone": "694201738",
        "lga": "Mystery",
      }
    ]; 

Now, if you want to group them by location, you can do that simply, like so:

var peopleByLocation = people.groupingBy('location');
var awka = peopleByLocation['Awka']; //List of all people with a 'location' : 'Awka'
var somewhereElse = peopleByLocation['Somewhere else'];

Here's a link to a slightly modified version in dartpad that you can play around with: https://dartpad.dev/8a53fc2eb4f63d904f414ea528574baf