House.dart

{
    "id": 1,
    "name": "Smith",
    "color": "Green",
    "pets": [
        {
            "id": 1,
            "breed": "Rottweiler",
            "name": "Mackie",
            "age": 8
        },
        {
            "id": 2,
            "breed": "Mastiff",
            "name": "Tanner",
            "age": 8
        }
    ]
}


class House {
  int id;
  String name;
  String color;
  List<Pets> pets;

  House({this.id, this.name, this.color, this.pets});

  House.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    color = json['color'];
    if (json['pets'] != null) {
      pets = new List<Pets>();
      json['pets'].forEach((v) {
        pets.add(new Pets.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['color'] = this.color;
    if (this.pets != null) {
      data['pets'] = this.pets.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class Pets {
  int id;
  String breed;
  String name;
  int age;

  Pets({this.id, this.breed, this.name, this.age});

  Pets.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    breed = json['breed'];
    name = json['name'];
    age = json['age'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['breed'] = this.breed;
    data['name'] = this.name;
    data['age'] = this.age;
    return data;
  }
}