I cannot figure out the way to adapt my dart model to my json. I constantly get the error in BreedInfo class, field height:

_TypeError (type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'String?')

I do not know why it does not accept a response if dynamic is supposed to identify the data type automatically and therefore would be a String anyway.

My dart model:

import 'dart:core';

class DogClass {
  Id? _iId;
  String? _breed;
  String? _origin;
  String? _url;
  String? _img;
  BreedInfo? _breedInfo;
  BreedInfo? _breedInfo1;
  List<String>? _behavior;

  DogClass(
      {Id? iId,
      String? breed,
      String? origin,
      String? url,
      String? img,
      BreedInfo? breedInfo,
      BreedInfo? breedInfo1,
      List<String>? behavior}) {
    if (iId != null) {
      this._iId = iId;
    }
    if (breed != null) {
      this._breed = breed;
    }
    if (origin != null) {
      this._origin = origin;
    }
    if (url != null) {
      this._url = url;
    }
    if (img != null) {
      this._img = img;
    }
    if (breedInfo != null) {
      this._breedInfo = breedInfo;
    }
    if (breedInfo1 != null) {
      this._breedInfo1 = breedInfo1;
    }
    if (behavior != null) {
      this._behavior = behavior;
    }
  }

  Id? get iId => _iId;
  set iId(Id? iId) => _iId = iId;
  String? get breed => _breed;
  set breed(String? breed) => _breed = breed;
  String? get origin => _origin;
  set origin(String? origin) => _origin = origin;
  String? get url => _url;
  set url(String? url) => _url = url;
  String? get img => _img;
  set img(String? img) => _img = img;
  BreedInfo? get breedInfo => _breedInfo;
  set breedInfo(BreedInfo? breedInfo) => _breedInfo = breedInfo;
  BreedInfo? get breedInfo1 => _breedInfo1;
  set breedInfo1(BreedInfo? breedInfo1) => _breedInfo1 = breedInfo1;
  List<String>? get behavior => _behavior;
  set behavior(List<String>? string) => _behavior = string;

  DogClass.fromJson(Map<String, dynamic> json) {
    _iId = json['_id'] != null ?  Id.fromJson(json['_id']) : null;
    _breed = json['breed'];
    _origin = json['origin'];
    _url = json['url'];
    _img = json['img'];
    _breedInfo = json['breed_info'] != null
        ? new BreedInfo.fromJson(json['breed_info'])
        : null;
    _breedInfo1 = json['breed_info1'] != null
        ? new BreedInfo.fromJson(json['breed_info1'])
        : null;
    if (json['behavior'] != null) {
      List<dynamic> _behavior = [];
      json['behavior'].forEach((v) {
        _behavior.add(Behavior.fromJson(v));
      });
    }
  }
}

class Id {
  String? _oid;

  Id({String? oid}) {
    if (oid != null) {
      _oid = oid;
    }
  }

  String? get oid => _oid;
  set oid(String? oid) => _oid = oid;

  Id.fromJson(Map<String, dynamic> json) {
    _oid = json['$oid'];
  }
}

class BreedInfo {
  String? _height;
  String? _weight;
  String? _coat;
  List<String>? _imgSrcSet;
  String? _lifeSpan;
  String? _otherNames;
  String? _commonNicknames;
  String? _colour;
  String? _litterSize;
  String? _notes;
  String? _breedStatus;
  String? _foundationStock;

  BreedInfo(
      {String? height,
      String? weight,
      String? coat,
      List<String>? imgSrcSet,
      String? lifeSpan,
      String? otherNames,
      String? commonNicknames,
      String? colour,
      String? litterSize,
      String? notes,
      String? breedStatus,
      String? foundationStock}) {
    if (height != null) {
      this._height = height;
    }
    if (weight != null) {
      this._weight = weight;
    }
    if (coat != null) {
      this._coat = coat;
    }
    if (imgSrcSet != null) {
      this._imgSrcSet = imgSrcSet;
    }
    if (lifeSpan != null) {
      this._lifeSpan = lifeSpan;
    }
    if (otherNames != null) {
      this._otherNames = otherNames;
    }
    if (commonNicknames != null) {
      this._commonNicknames = commonNicknames;
    }
    if (colour != null) {
      this._colour = colour;
    }
    if (litterSize != null) {
      this._litterSize = litterSize;
    }
    if (notes != null) {
      this._notes = notes;
    }
    if (breedStatus != null) {
      this._breedStatus = breedStatus;
    }
    if (foundationStock != null) {
      this._foundationStock = foundationStock;
    }
  }

  String? get height => _height;
  set height(String? height) => _height = height;
  String? get weight => _weight;
  set weight(String? weight) => _weight = weight;
  String? get coat => _coat;
  set coat(String? coat) => _coat = coat;
  List<String>? get imgSrcSet => _imgSrcSet;
  set imgSrcSet(List<String>? imgSrcSet) => _imgSrcSet = imgSrcSet;
  String? get lifeSpan => _lifeSpan;
  set lifeSpan(String? lifeSpan) => _lifeSpan = lifeSpan;
  String? get otherNames => _otherNames;
  set otherNames(String? otherNames) => _otherNames = otherNames;
  String? get commonNicknames => _commonNicknames;
  set commonNicknames(String? commonNicknames) =>
      _commonNicknames = commonNicknames;
  String? get colour => _colour;
  set colour(String? colour) => _colour = colour;
  String? get litterSize => _litterSize;
  set litterSize(String? litterSize) => _litterSize = litterSize;
  String? get notes => _notes;
  set notes(String? notes) => _notes = notes;
  String? get breedStatus => _breedStatus;
  set breedStatus(String? breedStatus) => _breedStatus = breedStatus;
  String? get foundationStock => _foundationStock;
  set foundationStock(String? foundationStock) =>
      _foundationStock = foundationStock;

  BreedInfo.fromJson(Map<String?, dynamic> json) {
    _height = json['height'];
    _weight = json['weight'];
    _coat = json['coat'];
    _lifeSpan = json['life_span'];
    _otherNames = json['other_names'];
    _commonNicknames = json['common_nicknames'];
    _colour = json['colour'];
    _litterSize = json['litter_size'];
    _notes = json['notes'];
    _breedStatus = json['breed_status'];
    _foundationStock = json['foundation_stock'];
  }

}

class Behavior {
  Id? _iId;
  String? _imageLink;
  int? _goodWithChildren;
  int? _goodWithOtherDogs;
  int? _shedding;
  int? _grooming;
  int? _drooling;
  int? _coatLength;
  int? _goodWithStrangers;
  int? _playfulness;
  int? _protectiveness;
  int? _trainability;
  int? _energy;
  int? _barking;
  int? _minLifeExpectancy;
  int? _maxLifeExpectancy;
  double? _maxHeightMale;
  double? _maxHeightFemale;
  int? _maxWeightMale;
  int? _maxWeightFemale;
  int? _minHeightMale;
  int? _minHeightFemale;
  int? _minWeightMale;
  int? _minWeightFemale;
  String? _breed;

  Behavior(
      {Id? iId,
      String? imageLink,
      int? goodWithChildren,
      int? goodWithOtherDogs,
      int? shedding,
      int? grooming,
      int? drooling,
      int? coatLength,
      int? goodWithStrangers,
      int? playfulness,
      int? protectiveness,
      int? trainability,
      int? energy,
      int? barking,
      int? minLifeExpectancy,
      int? maxLifeExpectancy,
      double? maxHeightMale,
      double? maxHeightFemale,
      int? maxWeightMale,
      int? maxWeightFemale,
      int? minHeightMale,
      int? minHeightFemale,
      int? minWeightMale,
      int? minWeightFemale,
      String? breed}) {
    if (iId != null) {
      this._iId = iId;
    }
    if (imageLink != null) {
      this._imageLink = imageLink;
    }
    if (goodWithChildren != null) {
      this._goodWithChildren = goodWithChildren;
    }
    if (goodWithOtherDogs != null) {
      this._goodWithOtherDogs = goodWithOtherDogs;
    }
    if (shedding != null) {
      this._shedding = shedding;
    }
    if (grooming != null) {
      this._grooming = grooming;
    }
    if (drooling != null) {
      this._drooling = drooling;
    }
    if (coatLength != null) {
      this._coatLength = coatLength;
    }
    if (goodWithStrangers != null) {
      this._goodWithStrangers = goodWithStrangers;
    }
    if (playfulness != null) {
      this._playfulness = playfulness;
    }
    if (protectiveness != null) {
      this._protectiveness = protectiveness;
    }
    if (trainability != null) {
      this._trainability = trainability;
    }
    if (energy != null) {
      this._energy = energy;
    }
    if (barking != null) {
      this._barking = barking;
    }
    if (minLifeExpectancy != null) {
      this._minLifeExpectancy = minLifeExpectancy;
    }
    if (maxLifeExpectancy != null) {
      this._maxLifeExpectancy = maxLifeExpectancy;
    }
    if (maxHeightMale != null) {
      this._maxHeightMale = maxHeightMale;
    }
    if (maxHeightFemale != null) {
      this._maxHeightFemale = maxHeightFemale;
    }
    if (maxWeightMale != null) {
      this._maxWeightMale = maxWeightMale;
    }
    if (maxWeightFemale != null) {
      this._maxWeightFemale = maxWeightFemale;
    }
    if (minHeightMale != null) {
      this._minHeightMale = minHeightMale;
    }
    if (minHeightFemale != null) {
      this._minHeightFemale = minHeightFemale;
    }
    if (minWeightMale != null) {
      this._minWeightMale = minWeightMale;
    }
    if (minWeightFemale != null) {
      this._minWeightFemale = minWeightFemale;
    }
    if (breed != null) {
      this._breed = breed;
    }
  }

  Id? get iId => _iId;
  set iId(Id? iId) => _iId = iId;
  String? get imageLink => _imageLink;
  set imageLink(String? imageLink) => _imageLink = imageLink;
  int? get goodWithChildren => _goodWithChildren;
  set goodWithChildren(int? goodWithChildren) =>
      _goodWithChildren = goodWithChildren;
  int? get goodWithOtherDogs => _goodWithOtherDogs;
  set goodWithOtherDogs(int? goodWithOtherDogs) =>
      _goodWithOtherDogs = goodWithOtherDogs;
  int? get shedding => _shedding;
  set shedding(int? shedding) => _shedding = shedding;
  int? get grooming => _grooming;
  set grooming(int? grooming) => _grooming = grooming;
  int? get drooling => _drooling;
  set drooling(int? drooling) => _drooling = drooling;
  int? get coatLength => _coatLength;
  set coatLength(int? coatLength) => _coatLength = coatLength;
  int? get goodWithStrangers => _goodWithStrangers;
  set goodWithStrangers(int? goodWithStrangers) =>
      _goodWithStrangers = goodWithStrangers;
  int? get playfulness => _playfulness;
  set playfulness(int? playfulness) => _playfulness = playfulness;
  int? get protectiveness => _protectiveness;
  set protectiveness(int? protectiveness) => _protectiveness = protectiveness;
  int? get trainability => _trainability;
  set trainability(int? trainability) => _trainability = trainability;
  int? get energy => _energy;
  set energy(int? energy) => _energy = energy;
  int? get barking => _barking;
  set barking(int? barking) => _barking = barking;
  int? get minLifeExpectancy => _minLifeExpectancy;
  set minLifeExpectancy(int? minLifeExpectancy) =>
      _minLifeExpectancy = minLifeExpectancy;
  int? get maxLifeExpectancy => _maxLifeExpectancy;
  set maxLifeExpectancy(int? maxLifeExpectancy) =>
      _maxLifeExpectancy = maxLifeExpectancy;
  double? get maxHeightMale => _maxHeightMale;
  set maxHeightMale(double? maxHeightMale) => _maxHeightMale = maxHeightMale;
  double? get maxHeightFemale => _maxHeightFemale;
  set maxHeightFemale(double? maxHeightFemale) =>
      _maxHeightFemale = maxHeightFemale;
  int? get maxWeightMale => _maxWeightMale;
  set maxWeightMale(int? maxWeightMale) => _maxWeightMale = maxWeightMale;
  int? get maxWeightFemale => _maxWeightFemale;
  set maxWeightFemale(int? maxWeightFemale) =>
      _maxWeightFemale = maxWeightFemale;
  int? get minHeightMale => _minHeightMale;
  set minHeightMale(int? minHeightMale) => _minHeightMale = minHeightMale;
  int? get minHeightFemale => _minHeightFemale;
  set minHeightFemale(int? minHeightFemale) =>
      _minHeightFemale = minHeightFemale;
  int? get minWeightMale => _minWeightMale;
  set minWeightMale(int? minWeightMale) => _minWeightMale = minWeightMale;
  int? get minWeightFemale => _minWeightFemale;
  set minWeightFemale(int? minWeightFemale) =>
      _minWeightFemale = minWeightFemale;
  String? get breed => _breed;
  set breed(String? breed) => _breed = breed;

  Behavior.fromJson(Map<String, dynamic> json) {
    _iId = json['_id'] != null ? new Id.fromJson(json['_id']) : null;
    _imageLink = json['image_link'];
    _goodWithChildren = json['good_with_children'];
    _goodWithOtherDogs = json['good_with_other_dogs'];
    _shedding = json['shedding'];
    _grooming = json['grooming'];
    _drooling = json['drooling'];
    _coatLength = json['coat_length'];
    _goodWithStrangers = json['good_with_strangers'];
    _playfulness = json['playfulness'];
    _protectiveness = json['protectiveness'];
    _trainability = json['trainability'];
    _energy = json['energy'];
    _barking = json['barking'];
    _minLifeExpectancy = json['min_life_expectancy'];
    _maxLifeExpectancy = json['max_life_expectancy'];
    _maxHeightMale = json['max_height_male'];
    _maxHeightFemale = json['max_height_female'];
    _maxWeightMale = json['max_weight_male'];
    _maxWeightFemale = json['max_weight_female'];
    _minHeightMale = json['min_height_male'];
    _minHeightFemale = json['min_height_female'];
    _minWeightMale = json['min_weight_male'];
    _minWeightFemale = json['min_weight_female'];
    _breed = json['breed'];
  }

}

my original json:

{  "_id": {    "$oid": "625f2900fe6aeb351381c3f3"  },  "breed": "Affenpinscher",  "origin": "Germany",  "url": "https://en.wikipedia.org/wiki/Affenpinscher",  "img": "https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Affenpinscher.jpg/220px-Affenpinscher.jpg",  "breed_info": {    "height": "23–30 cm (9–12 in)",    "weight": "3–6 kg (7–13 lb)",    "coat": "Wire",    "img_src_set": [      null,      {        "5x": "https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Affenpinscher.jpg/330px-Affenpinscher.jpg"      }    ],    "life_span": "Not available",    "other_names": "Not available",    "common_nicknames": "AffenAffie",    "colour": "Not available",    "litter_size": "Not available",    "notes": "Not available",    "breed_status": "Not available",    "foundation_stock": "Not available"  },  "breed_info1": {    "height": "23–30 cm (9–12 in)",    "weight": "3–6 kg (7–13 lb)",    "coat": "Wire",    "img_src_set": [      null,      {        "5x": "https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Affenpinscher.jpg/330px-Affenpinscher.jpg"      }    ],    "life_span": "Not available",    "other_names": "Not available",    "common_nicknames": "AffenAffie",    "colour": "Not available",    "litter_size": "Not available",    "notes": "Not available",    "breed_status": "Not available",    "foundation_stock": "Not available"  },  "string": [    {      "_id": {        "$oid": "625f2ba9fe6aeb351381c647"      },      "image_link": "https://api-ninjas.com/images/dogs/affenpinscher.jpg",      "good_with_children": 3,      "good_with_other_dogs": 3,      "shedding": 3,      "grooming": 3,      "drooling": 1,      "coat_length": 2,      "good_with_strangers": 5,      "playfulness": 3,      "protectiveness": 3,      "trainability": 3,      "energy": 3,      "barking": 3,      "min_life_expectancy": 12,      "max_life_expectancy": 15,      "max_height_male": 11.5,      "max_height_female": 11.5,      "max_weight_male": 10,      "max_weight_female": 10,      "min_height_male": 9,      "min_height_female": 9,      "min_weight_male": 7,      "min_weight_female": 7,      "breed": "Affenpinscher"    }  ]}

and how I fetch the data:

List<dynamic> BreedList = [];
var client = http.Client();

fetchData(url) async {
  final response = await client.get(Uri.parse(url));

  if (response.statusCode == 200) {
    var jsonDecoded = json.decode(response.body);
    BreedList = jsonDecoded
        .map((data) => DogClass.fromJson(data))
        .toList();
    return jsonDecoded;
  } else {
    throw Exception('Failed to load data');
  }
}


Solution 1: fsbelinda

In your class BreedInfo List<String>? _imgSrcSet; is wrong, it must be

List<Map<String, dynamic>>? _imgSrcSet
//or rather
List<Map<String, String>>? _imgSrcSet