Inner method in specific state is not recognized, BloC pattern - flutter

Question

I build a flutter project by using Bloc State management. But There are something that i don't understand. I know how to make State as Abstract class which it's implement for every it's children.
I have class state lake below, please focus to class MainHomeLoaded
abstract class MainHomeState extends Equatable{
MainHomeState();
}
class MainHomeUnInitialized extends MainHomeState{
#override
List<Object> get props => null;
}
class MainHomeLoading extends MainHomeState{
#override
List<Object> get props => null;
}
class MainHomeLoaded extends MainHomeState{
final List<Article> listArticle;
final bool hasReachedMax;
MainHomeLoaded({#required this.listArticle, this.hasReachedMax});
MainHomeLoaded copyWith({
List<Article> article,
bool hasReacedMax,
}){
return MainHomeLoaded(
listArticle: article ?? this.listArticle,
hasReachedMax: hasReacedMax ?? this.hasReachedMax);
}
#override
List<Object> get props => null;
}
class MainHomeError extends MainHomeState{
final String errorMsg;
MainHomeError({#required this.errorMsg});
#override
List<Object> get props => [errorMsg];
}
then i have MainHomeBloc class with implement Bloc method like mapEventtoState() and inside this method i made conditional like below(again please focus to conditional MainHomeLoaded):
#override
Stream<MainHomeState> mapEventToState(MainHomeEvent event) async*{
if(event is CallHomeLatestNews && !_hasReachedMax(state)){
if(state is MainHomeUnInitialized){
ResponseArticle responseArticle = await mainHomeRepository.latestNews(event.page);
if(responseArticle.status == 'success'){
List<Article> data = responseArticle.data;
yield MainHomeLoaded(listArticle: data);
}else{
yield MainHomeError(errorMsg: responseArticle.message);
}
}
if(state is MainHomeLoaded){
ResponseArticle responseArticle = await mainHomeRepository.latestNews(event.page);
if(responseArticle.status == 'success'){
List<Article> data = responseArticle.data;
yield data.isEmpty ? state.copyWith(hasReacedMax: true)
: MainHomeLoaded(listArticle: state.listArticle + data, hasReachedMax: false);
}
}
}
This is part that i don't understand at all, as you can see we have consider that state are in MainHomeLoaded because inside if conditional, but i got error building and my IDE show red line and also method copyWith()doesn't recognize. The error display like this:
what IDE says is
method copyWith() is not define for the class 'MainHomeState'
Can someone help me to give simple explanation for this case? Thanks
FYI i used Flutter in this version 1.12.13 and Dart version 2.7.0

Answer 1

Finally i found what my main problem. Perhaps it's bit different when we using state in BlocBuilder (in Screens) that automatically known specific state. So what i have to do is just casting it to be child that i wanted. So the solution of this case is like this:
if(state is MainHomeLoaded){
MainHomeLoaded mainHomeLoaded = state as MainHomeLoaded; // what i need
ResponseArticle responseArticle = await mainHomeRepository.latestNews(defaultPage);
if(responseArticle.status == 'success'){
List<Article> newData = responseArticle.data;
if(newData.isEmpty){
mainHomeLoaded.copyWith(hasReacedMax: true);
yield mainHomeLoaded;
}
defaultPage++;
}else{
print('gagal');
yield MainHomeError(errorMsg: responseArticle.message);
}
}
i hope it will help someone in future.