How can I get variable data into a Class with ChangeNotifier in Flutter? - flutter

Question

I have the following class which pulls in data from a remote JSON source, if I hardcode the URL into the class (daUrl) then it works just great.
But I am planning to use a variable URL which I want to feed into this class when I call it. But declaring the variable at the top just doesn't work.
Any ideas?
class ThreadData with ChangeNotifier
{
Map<String,dynamic> _map = {};
bool _error = false;
String _errorMessage = '';
int _isLoggedIn = 0;
int tid = 1836392;
Map<String,dynamic> get map => _map;
bool get error => _error;
String get errorMessage => _errorMessage;
int get isLoggedIn => _isLoggedIn;
//var daUrl = 'https://jsonplaceholder.typicode.com/todos/';
Future<void> get fetchData async {
final response = await post(Uri.parse(daUrl));
if ((response.statusCode == 200) && (response.body.length >0))
{
try
{
debugPrint('\Thread => Make Call => Success\n');
_map = json.decode(response.body);
_error = false;
}
catch(e)
{
_error = true;
_errorMessage = e.toString();
_map = {};
_isLoggedIn = 0;
}
}
else
{
_error = true;
_errorMessage = 'Error: It could be your internet connection';
_map = {};
_isLoggedIn = 0;
}
notifyListeners(); // if good or bad we will notify the listeners either way
}
void initialValues()
{
_map = {};
_error = false;
_errorMessage = '';
_isLoggedIn = 0;
notifyListeners();
}
}

Answer 1

You can pass it to its constructor:
class ThreadData with ChangeNotifier {
final String url;
// Defaults to some URL if not passed as parameter
ThreadData({this.url = 'https://jsonplaceholder.typicode.com/todos/'});
Map<String,dynamic> _map = {};
bool _error = false;
String _errorMessage = '';
int _isLoggedIn = 0;
int tid = 1836392;
Map<String,dynamic> get map => _map;
bool get error => _error;
String get errorMessage => _errorMessage;
int get isLoggedIn => _isLoggedIn;
Future<void> get fetchData async {
// Access the URL field here
final response = await post(Uri.parse(this.url));
if ((response.statusCode == 200) && (response.body.length >0))
{
try
{
debugPrint('\Thread => Make Call => Success\n');
_map = json.decode(response.body);
_error = false;
}
catch(e)
{
_error = true;
_errorMessage = e.toString();
_map = {};
_isLoggedIn = 0;
}
}
else
{
_error = true;
_errorMessage = 'Error: It could be your internet connection';
_map = {};
_isLoggedIn = 0;
}
notifyListeners(); // if good or bad we will notify the listeners either way
}
void initialValues()
{
_map = {};
_error = false;
_errorMessage = '';
_isLoggedIn = 0;
notifyListeners();
}
}
Then you can call it like that:
ThreadData(); // the URL will be https://jsonplaceholder.typicode.com/todos/
ThreadData(url: 'https://example.com'); // the URL will be https://example.com