How to map data if the key is numeric in flutter - flutter

Question

I am getting a response as key as numeric. How to map data for the following response
{
"1": [
{
"id": 6,
"name": "test 1"
},
{
"id": 8,
"name": "test 2"
},
{
"id": 7,
"name": "test 3"
}
],
"2": [
{
"id": 9,
"name": "ttt1"
},
{
"id": 5,
"name": "ttt3"
}
],
"3": [
{
"id": 4,
"name": "ttg",
"status_id": 1
}
]
}
Here is my model
import 'dart:convert';
Map<String, List<HomeBannerModel>> homeBannerModelFromJson(String str) => Map.from(json.decode(str)).map((k, v) => MapEntry<String, List<HomeBannerModel>>(k, List<HomeBannerModel>.from(v.map((x) => HomeBannerModel.fromJson(x)))));
String homeBannerModelToJson(Map<String, List<HomeBannerModel>> data) => json.encode(Map.from(data).map((k, v) => MapEntry<String, dynamic>(k, List<dynamic>.from(v.map((x) => x.toJson())))));
class HomeBannerModel {
int id;
String name;
HomeBannerModel({this.id, this.name});
HomeBannerModel.fromJson(Map<String, dynamic> json) {
id = json['id'];
name= json['name'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this.id;
data['name'] = this.name;
return data;
}
}
I need to take the value in UI as
var data1 = data['1'];
var data2= data['2'];
var data3= data['3'];
but I am getting errors. help how to get the data of each key in each of the variable
but while mapping I am getting errors I have added part of my code in UI
_message:"type 'Map<String, dynamic>' is not a subtype of type 'List'"

Answer 1

The following method will convert your json string to a valid map object so that you can get your data the way you wanted.
Map<String, List<HomeBannerModel>> homeBannerModelFromJson(String str) => Map.from(json.decode(str)).map((k, v) => MapEntry<String, List<HomeBannerModel>>(k, List<HomeBannerModel>.from(v.map((x) => HomeBannerModel.fromJson(x)))));
to access data
final data = homeBannerModelFromJson(your_json_string);
print(data['1'][0].name); // test 1

Answer 2

You current json structure is Map<String, List<Map<String, dynamic>>>
You can try something like
var json = {...};
json.forEach((key, list) {
list.forEach((homeBannerModelMap) {
HomeBannerModel hBM = HomeBannerModel.fromJson(homeBannerModelMap);
});
});

Answer 3

You getting the error because your data is the type of Map, not the List.
So you can do something like this:
// [data] is result banners
List data = [];
// [result] is your object variable {"1": [{"id": 1, "name": "Welcome!"}]} etc
// So .forEach method is used for iterating through your json object
result.forEach((k, v){
// in which iteration I will map every instance to List of [HomeBannerModel]
var value = v.map((banner) => HomeBannerModel.fromJson(banner)).toList();
//in result I will add the result to our [banners] List
data.add(value);
});
But in this case, you should do:
data1 = data[1] // use int as the key, result will be List of BannerModels [Instance of 'HomeBannerModel', Instance of 'HomeBannerModel']
instead of:
var data1 = data['1']; //use string as the key

Answer 4

Please try the following code with just one model 'HomeBannerModel'.
main() {
final Map<String, dynamic> json = {
"1": [
{"id": 6, "name": "test 1"},
{"id": 8, "name": "test 2"},
{"id": 7, "name": "test 3"}
],
"2": [
{"id": 9, "name": "ttt1"},
{"id": 5, "name": "ttt3"}
],
"3": [
{"id": 4, "name": "ttg", "status_id": 1}
]
};
final Map datas = {};
json.forEach((key, value) {
datas.addAll(
{"$key": value.map((ele) => HomeBannerModel.fromMap(ele)).toList()});
});
print(datas["1"]);
print(datas["2"]);
print(datas["3"]);
}
class HomeBannerModel {
final int id;
final String name;
final int status_id;
HomeBannerModel({
this.id,
this.name,
this.status_id,
});
Map<String, dynamic> toMap() {
return {
'id': id,
'name': name,
'status_id': status_id,
};
}
factory HomeBannerModel.fromMap(map) {
if (map == null) return null;
return HomeBannerModel(
id: map['id'],
name: map['name'],
status_id: map['status_id'],
);
}
#override
String toString() => 'Details(id: $id, name: $name, status_id: $status_id)';
}
You may also try with two models (1) Data and (2) HomeBannerModel. Please see the following code :
main() {
final Map<String, dynamic> json = {
"1": [
{"id": 6, "name": "test 1"},
{"id": 8, "name": "test 2"},
{"id": 7, "name": "test 3"}
],
"2": [
{"id": 9, "name": "ttt1"},
{"id": 5, "name": "ttt3"}
],
"3": [
{"id": 4, "name": "ttg", "status_id": 1}
]
};
final List<Data> data = [];
json.forEach((key, value) {
data.add(Data.fromMap({"id": key, "details": value}));
});
print(data.firstWhere((e) => e.dataID == '1').homeBannerModel);
print(data.firstWhere((e) => e.dataID == '2').homeBannerModel);
print(data.firstWhere((e) => e.dataID == '3').homeBannerModel);
}
class Data {
final String dataID;
final List<HomeBannerModel> homeBannerModel;
Data({
this.dataID,
this.homeBannerModel,
});
factory Data.fromMap(Map<String, dynamic> map) {
if (map == null) return null;
return Data(
dataID: map["id"],
homeBannerModel: (map["details"]
.map<HomeBannerModel>((ele) => HomeBannerModel.fromMap(ele))
.toList() as List<HomeBannerModel>));
}
#override
String toString() => 'Data(id: $dataID, details: $homeBannerModel)';
}
class HomeBannerModel {
final int id;
final String name;
final int status_id;
HomeBannerModel({
this.id,
this.name,
this.status_id,
});
Map<String, dynamic> toMap() {
return {
'id': id,
'name': name,
'status_id': status_id,
};
}
factory HomeBannerModel.fromMap(map) {
if (map == null) return null;
return HomeBannerModel(
id: map['id'],
name: map['name'],
status_id: map['status_id'],
);
}
#override
String toString() => 'Details(id: $id, name: $name, status_id: $status_id)';
}

Answer 5

From what I’m seeing in the sample response you shared , the kets are all string as should be... "1" is also String FYI.
Coming to the error you're getting its because you are probably using the var data1,data2,data3 as a map which it isn't.
var data1 = data['1'];
if you print this var you will get :
[
{
"id": 6,
"name": "test 1"
},
{
"id": 8,
"name": "test 2"
},
{
"id": 7,
"name": "test 3"
}
]
If you want to access the submap with id of 6 and name Test 1 do the following:
print(data1[0]);
to display name:
print(data1[0]["name"]);