Angularfire: Cannot create document reference with an auto-generated ID

[kespeart]

Version info

Angular:
"@angular/core": "^5.2.1",

Firebase:
CloudFirestore

AngularFire:
angularfire2 : "^5.0.0-rc.6"

Issue

I am unable to get a document reference with an auto generated id. Base on the cloudFirestore documentation it should be possible to do the following.

var newCityRef = db.collection('cities').doc();
// Later...
var setDoc = newCityRef.set({
    // ...
});

Currently, the the angularfire2 collection's doc() function has a mandatory parameter hence calling angularFirestore.collection('cities').doc() results in a typescript error.

Is this something the team is aware of? Are there plans to fix it?
Thanks

P.S
I know I can do collection angularFirestore.collection('cities').set({...}) which would auto generate a document id. However, I am trying to do a batch job which requires a document ref and my document is not pre-existing. Example

const batch = angularFirestore.firestore.batch();

const articleDocRef = angularFirestore.collection('articles').doc();
const journalistDocRef = angularFirestore.collection('journalist').doc('mike');

batch.set(articleDocRef, {'title': 'amazing article'});
batch.update(journalistDocRef, {'totalArticles': 200});
batch.commit()

In order for the above to work I have to get a docRef with an auto generated ID which is currently not possible.

[jamesdaniels]

Use AngularFirestore's createId() method for this.

[kespeart]

thanks

[stanemurhula]

Use AngularFirestore's createId() method for this.

Ok but how do we use the createId() method?
Can you share an example?