如何使用`combineReducers`在Dart中指定类型注释？

Question

I receive a message at the List from linter saying:

Specify type annotations

However I can't understand what type it wants. For Map I could get like so:

<String, String>{}

Where my Map is at the end, and I specify the type at the beginning, but I can't find the correct type for my reducer and my epics.

My current code:

final profileReducer = combineReducers<Profile>([
  TypedReducer<Profile, UpdateProfileBalanceAction>(_updateProfileBalance),
  TypedReducer<Profile, FetchProfileResultAction>(_setProfile),
]);

and:

final epics = combineEpics<AppState>([
  TypedEpic<AppState, FetchProfileAction>(profileEpic),
]);

Answer 1

The correct type I needed to use was:

final Function profileReducer = combineReducers<Profile>(
<Profile Function(Profile, dynamic)>[
  TypedReducer<Profile, FetchProfileResultAction>(_setProfile),
]);

But to make that more usable, I created a type:

import 'package:utgard/store/models/profile.dart';

typedef ProfileReducers = Profile Function(Profile, dynamic);

Then I can use in my reducers, like so:

final Function profileReducer = combineReducers<Profile>(<ProfileReducers>[
  TypedReducer<Profile, FetchProfileResultAction>(_setProfile),
]);

Answer 2

Dart doesn't support union type so typing actions properly won't be possible.. A "less realistic type" will be required

You can do the following:

final profileReducer = combineReducers<Profile>(<TypedReducer<Profile, Action>>[
  TypedReducer<Profile, UpdateProfileBalanceAction>(_updateProfileBalance),
  TypedReducer<Profile, FetchProfileResultAction>(_setProfile),
]);