如何在另一个组列表groupby中实现组列表是否可以在dart自定义对象中使用多个哈希码和operator ==

如何解决如何在另一个组列表groupby中实现组列表是否可以在dart自定义对象中使用多个哈希码和operator ==

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;

这在城镇或拉加之间的listView中是可能的，但我的问题是，我也想在这些位置中实现这些equals和hashCode，而在另一个ListView中则有所不同。

为简单起见，许多人具有相同的位置，但是我只需要一个位置，来自相同位置的许多人（作为标头），并在下面重复其名称。

有帮助吗？

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

当您查看此内容时，有些位置相同，即TownOrigin，lga。我的应用程序中有三个listView页面，它将分别显示来自同一位置，townOrigin，lga的所有那些（名称）。仅显示名称，但使用一个元素（如Awka所在位置）作为副标题。这同样适用于所有townOrigin和lga。期待获得帮助。

我的状况有所好转，但还没有解决我所有的问题， 使用此包sticky_grouped_list，https://pub.dev/packages/sticky_grouped_list

我想要一个小组内部的小组。我已经得到了一组LGA，但尚未放入LGA组中。

如何将“ Uga”等同一地点的人合并到一起。

解决方法

您可以尝试添加以下内容：

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;
  }
}

这将使您可以按特定字段对数据元素进行分组。

首先，将您的数据放入列表中

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

现在，如果要按位置对它们进行分组，则可以像这样简单地完成操作：

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

以下是dartpad中经过稍微修改的版本的链接，您可以使用它：https://dartpad.dev/8a53fc2eb4f63d904f414ea528574baf