View state from BehaviorSubject

view-state.ts

export class ViewState<T extends object> extends BehaviorSubject<T> {
  constructor(initialState: T) {
    super(initialState);
  }

  patch(newState: Partial<T>) {
    this.next({
      ...this.value,
      ...newState
    });
  }

  set(newState: T) {
    this.next(newState);
  }
}