component-communication-event.service.ts

import { Subject, Subscription } from 'rxjs';
import { filter, map } from 'rxjs/operators';
import { Injectable } from '@angular/core';

@Injectable({
    providedIn: 'root'
})
export class ComponentCommunicationEventService {

    // create a subject to hold data which can be subscribed to.
    // you only get the data after you subscribe.
    private _subject$ = new Subject();

    // used in the listening component.
    // i.e. this.componentCommunicationEventService = this._componentCommunicationEventService.on(Events.loginSuccess, () => doSomething());
    on(event: Events, action: () => void): Subscription {
        return this._subject$
            .pipe(
                // filter down based on event name to any events that are emitted out of the subject from the emit method below.
                filter((e: EmitEvent) => e.name === event),
                map((e: EmitEvent) => e.value)
            )
            .subscribe(action); // subscribe to the subject to get the data.
    }

    // used in the emitting component.
    // i.e. this.componentCommunicationEventService.emit(new EmitEvent(Events.loginSuccess));
    emit(event: EmitEvent) {
        this._subject$.next(event);
    }
}

export class EmitEvent {
    constructor(public name: any, public value?: any) { }
}

// possible events that can be emitted.
export enum Events {
    loginSuccess,
    gravSearchExecuted,
    projectCreated
}