Parsing from json call to map in flutter

Question

Hi the following dart code in flutter, make a rest call to a node.js server returning a map of values in a map. When I run the code, however, the exception below is raised. How can I go about solving this? Below is an example of json values returning from the rest server in node.js.

Dart Code:

  static Future<Map> Ricerca(Utente u, int IdCantiere, String NomeCantiere,
      String RagioneSociale, bool isUtente) async {

    Map ret;
    Map map = {
      'IdUtente': u.GetIdUtente(),
      'IdCantiere': IdCantiere,
      'NomeCantiere': NomeCantiere,
      'RagioneSociale': RagioneSociale,
      'CheckBoxCantieriCreatiDaUtenteLoggato': isUtente
    };
    String value = await apiRequest("/cantieri/ricerca", map);

    ret = json.decode(value);
          return ret;
  }

Exception:

[VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'Map<dynamic, dynamic>'
#0      CantiereController.Ricerca (package:MyApp/Controller/Cantiere.dart:28:5)
<asynchronous suspension>
#1      Cantiere.ricerca (package:MyApp/Model/Cantiere.dart:18:142)
#2      inizializzaValori (package:MyApp/View/Cantieri/training_screen.dart:25:38)
<asynchronous suspension>
#3      _TrainingScreenState.initState (package:MyApp/View/Cantieri/training_screen.dart:47:5)
#4      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4355:58)
#5      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4201:5)
#6      Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
#7      MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5551:32)
#8      Element.inflateWidget (package:flutter/src/widgets/framework.dart:3194:14)
#9      Element.updateChild (package:flutter/src/widgets/framework.dart:2988<…>MyApp

ApiRest.dart Code:

Future<String> apiRequest(String urlpassed, Map jsonMap) async {
  //Give server and port
  String server = await Storage.leggi("Server");
  String porta = await Storage.leggi("Porta");

  var url=""+server+":"+porta;

  url=url+urlpassed;
  HttpClient httpClient = new HttpClient();

  HttpClientRequest request = await httpClient.postUrl(Uri.parse(url));
  request.headers.set('content-type', 'application/json');
  request.add(utf8.encode(json.encode(jsonMap)));
  HttpClientResponse response = await request.close();

  String reply = await response.transform(utf8.decoder).join();
  httpClient.close();
  return reply;
}

JSON Example:

[
    {
        "IdCantiere": 4,
        "IdCliente": 40,
        "Filiale": "SEDE",
        "RagioneSociale": "dsdso",
        "NomeCantiere": "sala sdsd",
        "DataCreazioneCantiere": "2017-08-04T18:20:31.333Z",
        "Tipologia": "Consuntivo",
        "StatoCantiere": "Chiuso",
        "StatoFatturazione": 1,
        "DescrizioneEstesa": "sddsdsd"
    },
    {
        "IdCantiere": 5,
        "IdCliente": 204,
        "Filiale": "SEDE",
        "RagioneSociale": "sdsds",
        "NomeCantiere": "manutenzione allarme",
        "DataCreazioneCantiere": "2017-08-04T18:27:42.017Z",
        "Tipologia": "Consuntivo",
        "StatoCantiere": "Chiuso",
        "StatoFatturazione": 1,
        "DescrizioneEstesa": "manutenzione impianto allarme AVS"
    },
    {
        "IdCantiere": 6,
        "IdCliente": 140,
        "Filiale": "SEDE",
        "RagioneSociale": "Psdsddo",
        "NomeCantiere": "Ristrutturazione terremoto",
        "DataCreazioneCantiere": "2017-08-07T17:45:15.347Z",
        "Tipologia": "Consuntivo",
        "StatoCantiere": "Chiuso",
        "StatoFatturazione": 1,
        "DescrizioneEstesa": "        stampato 10/01/19"
    }
]

Having your code in Italian is going to make any one helping you have a very hard time. — J. S.
– J. S., Commented Feb 17, 2020 at 15:30

Sebastian · Accepted Answer · 2020-02-17 15:49:24Z

1

Try

Map<String, dynamic> ret = json.decode(value);

answered Feb 17, 2020 at 15:49

Sebastian

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6 Comments

Sebastian Over a year ago

Can you provide an example of the response of await apiRequest("/cantieri/ricerca", map); ?

Sebastian Over a year ago

I meant the json value that is returned from the request and then passed to json.decoded

Sebastian Over a year ago

Try List<Map<String, dynamic>> ret = json.decode(value);

riki Over a year ago

I tried your solution I have this error: ui_dart_state.cc(157)] Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'List<Map<String, dynamic>>'

Sebastian Over a year ago

If you do this it'll probably work var ret = json.decode(value);

|

Enzo Lizama · Accepted Answer · 2020-02-17 16:23:05Z

0

The rest service is returning a list of Map and you method is awaiting for just a Map, probably change your method like the code below could help


static Future<List<Map<String,dynamic>>> Ricerca(Utente u, int IdCantiere, String NomeCantiere,
      String RagioneSociale, bool isUtente) async {

    Map ret;
    Map map = {
      'IdUtente': u.GetIdUtente(),
      'IdCantiere': IdCantiere,
      'NomeCantiere': NomeCantiere,
      'RagioneSociale': RagioneSociale,
      'CheckBoxCantieriCreatiDaUtenteLoggato': isUtente
    };
    String value = await apiRequest("/cantieri/ricerca", map);

    ret = json.decode(value);
          return ret;
  }

answered Feb 17, 2020 at 16:23

Enzo Lizama

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2 Comments

riki Over a year ago

I tried your solution I have this error: ui_dart_state.cc(157)] Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'List<Map<String, dynamic>>'

Enzo Lizama Over a year ago

Try with the suggestion, replace 'List<Map<String, dynamic>> with List<dynamic> , what happens?

Brian Gorman · Accepted Answer · 2020-02-17 16:40:38Z

0

Your JSON is returning a List not a Map. Keep it a List:

List<dynamic> ret = json.decode(value);

Then you can change the list type:

List<Map<String, dynamic>> data = ret.map((value) => value as Map<String, dynamic>).toList();

answered Feb 17, 2020 at 16:40

Brian Gorman

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