Update state of an object in Riverpod - flutter

Question

I want to update a state of an object and notify to update the UI accordingly.
For example
import 'package:riverpod_annotation/riverpod_annotation.dart';
class CounterState {
int value;
bool isCompleted;
CounterState({this.value = 0, this.isCompleted = false});
}
#riverpod
class CounterProvider extends _$CounterProvider {
#override
CounterState build() {
return CounterState;
}
void setValue(int newValue) {
state.value = newValue;
if (newValue == 1) {
state.isCompleted = true;
}
}
}
I use CounterState to contain all the necessary state of for 1 page. As this method doesn't work, and only works if I use this
if (newValue == 1) {
state = CounterState(value: newValue, isCompleted: true);
}
As if the state object become more and more complex, I want to keep other variable in the state remain the same, and only update the one I need, for the example above I can use something like this
if (___) {
state = CounterState(value: state.value, isCompleted: true);
}
But it is going to be difficult to update the state if CounterState have 10 variables or more.
Is there a way to overcome this?

Answer 1

Try implementing the copyWith method
class CounterState {
int value;
bool isCompleted;
CounterState({
this.value = 0,
this.isCompleted = false
});
CounterState copyWith({ int? value, bool? isCompleted }) => CounterState(
value: value ?? this.value,
isCompleted: isCompleted ?? this.isCompleted
);
}
With that done, you can just do:
state = state.copyWith(value: newValue, isCompleted: true, ...);
And just specify the fields you would like to update.