title: Angular 10 async bidirectional inter component comunication
body: <p>I have a ParentComponent and it contains a number of ChildComponents. The ChildComponent exposes an EventEmitter via <code>@Output()</code>. I use that to emit some data that is gathered from a form contained by the ChildComponent.</p>
  <p>The ParentComponent has the means to asynchronously save the data to my backend server but the problem is, I need to somehow send back to the ChildComponent the results of the save operation so that it may close the form or show validation errors.</p>
  <p>I'm thinking about creating some sort of Subject in my child component and emitting that together with the actual data and on the parent side I would get the emitted stuff, use the data to send to the server, and use the <code>Subject</code> to publish data back to the child component but it seems awfully convoluted and ugly.</p>
  <p>If I were to use an <code>@Input</code> on the child component in order to receive updates for this from the ParentComponent then the parent would have to know which of the children emitted the data and that doesn't seem nice.</p>
  <p>What nice solutions are there to ensure async bidirectional communication between parent and child components?</p>