export interface Subject {
    notify: (subjectName: string) => Promise<void>;
    attach: (observer: Observer) => void;
}
export interface Observer {
    update: (data: object, subjectName: string | null) => Promise<void>;
    attach: (subject: Subject) => void;
}
/**
 * It may look like there is some confusion on the Observer pattern.
 * Actually I'm still thinking about who's gonna listen:
 * - each field for itself, or
 * - the form as a delegate
 */