ephemeral_value 1.3.0

Ephemeral value types for Dart and Flutter. Easily represent loading, success, error, empty, and initial states in your app logic and UI.

example/README.md

Example

Sample state class

The state class holds the current state of your feature or screen. Here, the LoginState contains an Ephemeral<User> to represent the user data and its ephemeral state. By default, it starts with a NoneValue, and you can use copyWith to update the state immutably.

class LoginState {
    final Ephemeral<User> user;

    LoginState({
        this.user = const NoneValue(null),
    });

    const LoginState copyWith({
        Ephemeral<User>? user,
    }) {
        return LoginState(
            user: user ?? this.user,
        );
    }
}

Sample bloc logic

This section demonstrates how to update the state in response to asynchronous events, such as loading a user. The state transitions through LoadingValue, SuccessValue, and ErrorValue depending on the outcome of the operation.

try {
    emit(state.copyWith(user: LoadingValue(null)));
    final user = await UserRepository().getUser(event.id);
    emit(state.copyWith(user: SuccessValue(user)));
} catch (e) {
    emit(state.copyWith(user: ErrorValue(null, e)));
    // or you can also use one of the provided transition method
    emit(state.copyWith(user: state.user.toError()));
}

Sample widget Code

In your widget, you can do type checks on the Ephemeral state to render different UI components based on the current state of the user data. This allows you to handle loading, success, and error states effectively.

if (state.user is LoadingValue) {
    return const CircularProgressIndicator();
} else if (state.user is SuccessValue) {
    return Text('User: ${(state.user as SuccessValue).value.name}');
} else if (state.user is ErrorValue) {
    return Text('Error: ${(state.user as ErrorValue).error}');
}