testeJson.dart

import 'dart:convert';

void main() {
//  jsonSemList();

  jsonComList();
  
//   lm.m!.add(Msg('3333'));
//   lmJson = jsonEncode(lm);
//   print(lmJson);
}

void testeDate() {
  var ts = DateTime.now().millisecondsSinceEpoch; 
  var d = DateTime.fromMillisecondsSinceEpoch(ts);
  print('dia: ${d.day} hora: ${d.hour}:${d.minute}:${d.second}');  
}

void jsonSemList() {
  String js = jsonEncode(Msg('111'));
  print('encode: $js');
  Map<String, dynamic> m = jsonDecode(js);
  print('decode: ${m['x']}');  
}

void jsonComList() {
  List<Msg> l = [];
  l.add(Msg('1111'));
  l.add(Msg('2222'));
  ListMsg lm = ListMsg(l);
  var lmJson = jsonEncode(lm);
  print(lmJson);
  Map<String, dynamic> map = jsonDecode(lmJson);
  List<dynamic> l1 = map['xl'];
  var s = Msg('3333').toJson();
  l1.add(s);
  l.clear();
  for (Map<String, dynamic> x in l1) {
    Msg m = Msg(x['x']);
    l.add(m);
  }
  for (Msg m in lm.m!) {
    print('msg-> ${m.x}');
  }
  print(jsonEncode(lm));
}

class Msg {
  final String x;
  Msg(this.x);
  Map<String, dynamic> toJson() => { 'x': x };
  Msg.fromJson(Map<String, dynamic> json)
    : x = json['x']; 
}

class ListMsg {
  final List<Msg>? m;
  ListMsg(this.m);
  Map<String, dynamic> toJson() => { 'xl': m };
  ListMsg.fromJson(Map<String, dynamic> json)
    : m = json['xl'] != null ? List<Msg>.from(json['xl']) : null;   
}