How to use generics and list of generics with json serialization in Dart?

Here's a example about that

https://github.com/dart-lang/json_serializable/blob/master/example/lib/json_converter_example.dart

// json_converter_example.dart

// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file// for details. All rights reserved. Use of this source code is governed by a// BSD-style license that can be found in the LICENSE file.import 'package:json_annotation/json_annotation.dart';part 'json_converter_example.g.dart';@JsonSerializable()class GenericCollection<T> {  @JsonKey(name: 'page')  final int page;  @JsonKey(name: 'total_results')  final int totalResults;  @JsonKey(name: 'total_pages')  final int totalPages;  @JsonKey(name: 'results')  @_Converter()  final List<T> results;  GenericCollection(      {this.page, this.totalResults, this.totalPages, this.results});  factory GenericCollection.fromJson(Map<String, dynamic> json) =>      _$GenericCollectionFromJson<T>(json);  Map<String, dynamic> toJson() => _$GenericCollectionToJson(this);}class _Converter<T> implements JsonConverter<T, Object> {  const _Converter();  @override  T fromJson(Object json) {    if (json is Map<String, dynamic> &&        json.containsKey('name') &&        json.containsKey('size')) {      return CustomResult.fromJson(json) as T;    }    if (json is Map<String, dynamic> &&        json.containsKey('name') &&        json.containsKey('lastname')) {      return Person.fromJson(json) as T;    }    // This will only work if `json` is a native JSON type:    //   num, String, bool, null, etc    // *and* is assignable to `T`.    return json as T;  }  @override  Object toJson(T object) {    // This will only work if `object` is a native JSON type:    //   num, String, bool, null, etc    // Or if it has a `toJson()` function`.    return object;  }}@JsonSerializable()class CustomResult {  final String name;  final int size;  CustomResult(this.name, this.size);  factory CustomResult.fromJson(Map<String, dynamic> json) =>      _$CustomResultFromJson(json);  Map<String, dynamic> toJson() => _$CustomResultToJson(this);  @override  bool operator ==(Object other) =>      other is CustomResult && other.name == name && other.size == size;  @override  int get hashCode => name.hashCode * 31 ^ size.hashCode;}@JsonSerializable()class Person {  final String name;  final String lastname;  Person(this.name, this.lastname);  factory Person.fromJson(Map<String, dynamic> json) => _$PersonFromJson(json);  Map<String, dynamic> toJson() => _$PersonToJson(this);  @override  bool operator ==(Object other) =>      other is Person && other.name == name && other.lastname == lastname;}

// main.dart

import './json_converter_example.dart';import 'dart:convert';final jsonStringCustom =    '''{"page":1,"total_results":10,"total_pages":200,"results":[{"name":"Something","size":80},{"name":"Something 2","size":200}]}''';final jsonStringPerson =    '''{"page":2,"total_results":2,"total_pages":300,"results":[{"name":"Arya","lastname":"Stark"},{"name":"Night","lastname":"King"}]}''';void main() {  // Encode CustomResult  List<CustomResult> results;  results = [CustomResult("Mark", 223), CustomResult("Albert", 200)];  // var customResult = List<CustomResult> data;  var jsonData = GenericCollection<CustomResult>(      page: 1, totalPages: 200, totalResults: 10, results: results);  print({'JsonString', json.encode(jsonData)});  // Decode CustomResult  final genericCollectionCustom =      GenericCollection<CustomResult>.fromJson(json.decode(jsonStringCustom));  print({'name', genericCollectionCustom.results[0].name});  // Encode Person  List<Person> person;  person = [Person("Arya", "Stark"), Person("Night", "King")];  var jsonDataPerson = GenericCollection<Person>(      page: 2, totalPages: 300, totalResults: 2, results: person);  print({'JsonStringPerson', json.encode(jsonDataPerson)});  // Decode Person  final genericCollectionPerson =      GenericCollection<Person>.fromJson(json.decode(jsonStringPerson));  print({'name', genericCollectionPerson.results[0].name});}

the result it's

{JsonStringCustom, {"page":1,"total_results":10,"total_pages":200,"results":[{"name":"Mark","size":223},{"name":"Albert","size":200}]}}{name, Something}{JsonStringPerson, {"page":2,"total_results":2,"total_pages":300,"results":[{"name":"Arya","lastname":"Stark"},{"name":"Night","lastname":"King"}]}}{name, Arya}

here is the my proper solution perfectly worked for me.

class Paginate<T> {  int from;  int index;  int size;  int count;  int pages;  List<T> items;  bool hasPrevious;  bool hasNext;  Paginate(      {this.index,      this.size,      this.count,      this.from,      this.hasNext,      this.hasPrevious,      this.items,      this.pages});  factory  Paginate.fromJson(Map<String,dynamic> json,Function fromJsonModel){    final items = json['items'].cast<Map<String, dynamic>>();    return Paginate<T>(      from: json['from'],      index: json['index'],      size: json['size'],      count: json['count'],      pages: json['pages'],      hasPrevious: json['hasPrevious'],      hasNext: json['hasNext'],      items: new List<T>.from(items.map((itemsJson) => fromJsonModel(itemsJson)))    );  }}

Lets say we are going to use flight model paginate model. here you must configure the flight list.

class Flight {  String flightScheduleId;  String flightId;  String flightNo;  String flightDate;  String flightTime;  Flight(      {this.flightScheduleId,      this.flightId,      this.flightNo,      this.flightDate,      this.flightTime});  factory Flight.fromJson(Map<String, dynamic> parsedJson) {    var dateFormatter = new DateFormat(Constants.COMMON_DATE_FORMAT);    var timeFormatter = new DateFormat(Constants.COMMON_TIME_FORMAT);    var parsedDate = DateTime.parse(parsedJson['flightDepartureTime']);    String formattedDate = dateFormatter.format(parsedDate);    String formattedTime = timeFormatter.format(parsedDate);    return Flight(        flightScheduleId: parsedJson['id'],        flightId: parsedJson['flightLayoutId'],        flightNo: parsedJson['outboundFlightName'],        flightDate: formattedDate,        flightTime: formattedTime,  }  // Magic goes here. you can use this function to from json method.  static Flight fromJsonModel(Map<String, dynamic> json) => Flight.fromJson(json);}

-> Here you can use,

 Paginate<Flight>.fromJson(responses, Flight.fromJsonModel);