Fetching pHp array or map as JSON data in Flutter? - php

Question

I am trying to fetch some data from server using json in my flutter app. This is the function I am using.
List<String> userFriendList = ["No Friends"];
Future<http.Response> _fetchSampleData() {
return http.get('//link/to/server/fetcher/test_fetcher.php');
}
Future<void> getDataFromServer() async {
final response = await _fetchSampleData();
if (response.statusCode == 200) {
Map<String, dynamic> data = json.decode(response.body);
userLvl = data["lvl"].toString();
userName = data["name"];
userFriendList = List();
userFriendList = data["friendlist"];
} else {
// If the server did not return a 200 OK response,
// then throw an exception.
print('Failed to load data from server');
}
}
I get the usrLvl and userName right. But for userFriendList, I get the following error:
[ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'List<String>'
Code on the server end (test_fetcher.php) :
<?php
$myObj->name = "JohnDoe";
$myObj->lvl = 24;
$friends = array("KumarVishant", "DadaMuni", "BabuBhatt", "BesuraGayak", "BabluKaneria", "MorrisAbhishek", "GoodLuckBaba", "ViratKohli", "LeanderPaes");
$myObj->friendlist = $friends;
header('Content-Type: application/json');
$myJSON = json_encode($myObj);
echo $myJSON;
?>

Answer 1

This is a cast error: List<dynamic> != List<String>
You can convert / cast your list in several ways.
I advise you to use this library to simplify your json / Dart object conversion
: https://pub.dev/packages/json_serializable
json_serializable will generate the conversion methods (fromJson and toJson) and take care of everything.
It's easier and safer than doing it manually.

Answer 2

Just what the error says. The userFriendList is of type List you have it as List.
List<String> userFriendList = ["No Friends"];
Should be
List<dynamic> userFriendList = [];
Or a different list entirely if this doesn't work for you.

Answer 3

The error explains it. The fetched data from the server api is decoded to type List<dynamic> and you declared userFriendList to be of type List<String>. What you need to do is change the type of userFriendList from
List<String> userFriendList = ["No Friends"];
to:
List<dynamic> userFriendList = [];