How to deserialize an Object from Map (DART)-CodePudding

how can I re-create objects from a serialized/deserialized map of objects?

import 'dart:convert';

class InternalTx {
  int a;
  bool b;

  InternalTx(this.a, this.b);

  factory InternalTx.fromJson(Map<String, dynamic> json) =>
      InternalTxFromJson(json);

  Map<String, dynamic> toJson() => InternalTxToJson(this);
}

InternalTx InternalTxFromJson(Map<String, dynamic> json) => InternalTx(
      json['a'] as int,
      json['b'] as bool,
    );

Map<String, dynamic> InternalTxToJson(InternalTx instance) => <String, dynamic>{
      'a': instance.a,
      'b': instance.b,
    };

main() {
  Map<String, InternalTx> m = {};
  for (int i=0; i<10; i  )
  {
    InternalTx itx = InternalTx(i, false);
    m["Hello: $i"] = itx;
  }
  
  String serM = jsonEncode(m);
  print(serM);
  
  ////SERILIZED OKAY
  
  Map<String, dynamic> n = jsonDecode(serM);
  InternalTx newItx = n["Hello: 0"];      <-- Problem here.
  print(newItx);
}

Output:

{"Hello: 0":{"a":0,"b":false},"Hello: 1":{"a":1,"b":false},"Hello: 2":{"a":2,"b":false},"Hello: 3":{"a":3,"b":false},"Hello: 4":{"a":4,"b":false},"Hello: 5":{"a":5,"b":false},"Hello: 6":{"a":6,"b":false},"Hello: 7":{"a":7,"b":false},"Hello: 8":{"a":8,"b":false},"Hello: 9":{"a":9,"b":false}}
Uncaught Error: TypeError: Instance of '_JsonMap': type '_JsonMap' is not a subtype of type 'InternalTx'

What is missing here to deserialize the map of objects correctly? Thanks!

CodePudding user response：

You need to actually call the InternalTx.fromJson constructor since this is not done automatically. So your last piece of code should be:

  ////SERILIZED OKAY
  Map<String, dynamic> n = jsonDecode(serM);
  InternalTx newItx = InternalTx.fromJson(n["Hello: 0"]);
  print(newItx); // Instance of 'InternalTx'