How do you serialize/parse a nested JSON array in Flutter/Dart if it has no name/key

Question

I'm working with a RESTful API that seems to be working and used in other applications that gives me something like this:

 "notes": [
    [
      {
        "automaticNote": false,
        "contactId": 0,
        "caseFileId": 0,
        "dateCreated": "2019-05-02",
        "deletedTime": "2019-05-02T19:31:54.588Z"
      }
    ]
  ]

The double pair of square brackets means that one pair of the square brackets has no name/key associated with it. To make matters worse, notes is itself nested in some complex JSON.

I tried using JSON to Dart but it throws an error. So really my question is, how do I serialize a JSON array that has no key/name?

I'd normally do it like this:

    class Note {
  bool automaticNote;
  int contactId;
  int caseFileId;
  String dateCreated;
  String deletedTime;

  Note(
      {this.automaticNote,
      this.contactId,
      this.caseFileId,
      this.dateCreated,
      this.deletedTime});

  Note.fromJson(Map<String, dynamic> json) {
    automaticNote = json['automaticNote'];
    contactId = json['contactId'];
    caseFileId = json['caseFileId'];
    dateCreated = json['dateCreated'];
    deletedTime = json['deletedTime'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['automaticNote'] = this.automaticNote;
    data['contactId'] = this.contactId;
    data['caseFileId'] = this.caseFileId;
    data['dateCreated'] = this.dateCreated;
    data['deletedTime'] = this.deletedTime;
    return data;
  }
}

But the double JSON array is throwing me off (and again, notes itself is nested in a more complex JSON object but for the sake of simplicity I did not include the whole thing here).

Thanks!

Richard Heap · Accepted Answer · 2019-05-03 02:13:05Z

2

After decoding, notes is a member of some Map<String, dynamic> as usual. Let's call that m.

So m['notes'] is a list, who's first member, m['notes'][0] is also a list. Its first member, m['notes'][0][0] is another Map<String, dynamic>, which is what you need for your constructor.

You should therefore be able to use:

Note n = Note.fromJson(m['notes'][0][0]);

answered May 3, 2019 at 2:13

Richard Heap

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1 Comment

Nomnom Over a year ago

Wow I think this might solve it! I'll give it a try and let you know. Thank you so much!

DraeRyte · Accepted Answer · 2020-10-26 19:51:05Z

Let's take the case of you saving automaticNote;

automaticNote = json['notes'][0][0]['automaticNote'];

This offers the key for notes which has an array where your data is at the first point or index 0 (of notes hence [0]) and within that array there is another array which has your data. Again it's the first array item so, [0] and then you're finally at the level with your data so you then use your key for automaticNote, ['automaticNote'].

Note.fromJson(Map<String, dynamic> json) {
    automaticNote = json[0][0]['automaticNote'];
    contactId = json[0][0]['contactId'];
    caseFileId = json[0][0]['caseFileId'];
    dateCreated = json[0][0]['dateCreated'];
    deletedTime = json[0][0]['deletedTime'];
  }

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