Objective is to convert a String to List using map and return the value to a function call.
I am using SharedPreferences to save a list of object called where in I save the data at a point and get the data when it is to be put on view.
The below block is the function where the error is occurring.
void getData() async {
final prefs = await SharedPreferences.getInstance();
final String taskString = prefs.getString('task_data').toString();
List<Task> tasksData = Task.decode(taskString);
_tasks = tasksData;
notifyListeners();
}
decode() looks basically does the conversion.
static List<Task> decode(String tasks) {
return (jsonDecode(tasks) as List<dynamic>).map<Task>((task) {
return Task.fromJson(task);
}).toList();
It advises to check for null condition in type cast of decode(). But on performing the check, it gives the same error.
your response might be not a proper map so it cannot decode that data using the jsonDecode function so it returns Null, so you can use your function like this might be helpful for you :
static List<Task> decode(String tasks) {
var data = (jsonDecode(tasks) as List<dynamic>?);
if(data != null){
return (jsonDecode(tasks) as List<dynamic>?)!.map<Task>((task) {
return Task.fromJson(task);
}).toList();
} else {
return <Task>[];
}
}