I’m trying to use Flutter documentation to map an array data (comes from API) to the dart object. The documentation uses a single Json object, not an array. I have the following codes:
Json data:
[
{
"channelId" : 1
"channelTitle" : "Photos"
"channelImage" : pr01.jpg
"channelLastPost" : null
"lastUpdate" : null
"userRef" : 1
},
{
"channelId" : 2
"channelTitle" : "Science"
"channelImage" : pr02.jpg
"channelLastPost" : "For test ...."
"lastUpdate" : "2023-01-03"
"userRef" : 1
}
]
ChannelListModel.dart:
class ChannelListModel {
String creator;
String? image;
String title;
String lastPost;
String lastUpdate;
ChannelListModel(
{required this.creator,
required this.image,
required this.title,
required this.lastPost,
required this.lastUpdate});
factory ChannelListModel.fromJson(Map<String, dynamic> json) {
return ChannelListModel(
creator: json['userRef'],
image: json['channelImage'],
title: json['channelTitle'],
lastPost: json['channelLastPost'],
lastUpdate: json['lastUpdate']);
}
Map<String, dynamic> toJson() {
return {
"userRef" : creator,
"channelImage" : image,
"channelTitle" : title,
"channelLastPost" : lastPost,
"lastUpdate" : lastUpdate
};
}
}
HttpRequest.dart:
class HttpServices {
Future<List<ChannelListModel>> getChannelList() async {
var url = base.BaseURL.channelListUrl;
final response = await http.get(Uri.parse(url));
if (response.statusCode == 200) {
// If the server did return a 200 OK response,
// then parse the JSON.
return List<ChannelListModel>.fromJson(jsonDecode(response.body)); //I have problem in this line
} else {
// If the server did not return a 200 OK response,
// then throw an exception.
throw Exception('Failed to load album');
}
}
}
ChannelPage.dart:
class _ChannelsState extends State<Channels> {
List<ChannelListModel> channels = [];
@override
void initState() {
super.initState();
channels = getChannelsFromHttp(); // A valid array object needs to be provided here.
}
getChannelsFromHttp()async{
var httpService = HttpServices();
var result = await httpService.getChannelList();
return result;
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: ListView.builder(
itemCount: channels.length,
itemBuilder: (context, index) =>
ChannelCard(channelModel: channels[index]),
),
);
}
}
I want to classify my codes so I decided to provided different dart files for each part. How can I fix my code?
3
Answers
Instead of
returnList<ChannelListModel>.fromJson(jsonDecode(response.body));
Try this code,
Added based on comments
Your
fromJson
factory returns singleChannelListModel
.You can’t use
List<ChannelListModel>.fromJson
. Instead iterate throughList
and convert eachjson
toChannelListModel
You can modify the ChannelListModel.fromJson method to handle a list of JSON objects instead of a single object. Here’s one way to do it:
You can also use jsonDecode to convert the response body to a List and then use the above method to convert the list to ChannelListModel
Also, you need to update the getChannelsFromHttp function to assign the result of httpService.getChannelList() to channels variable instead of calling the function again.
This should solve the problem in your code.