Reactive Firebase / BASICS - RxFire, Getting documents

ydkf-rf00.ts

/* Getting a single firestore document */
import { docData } from 'rxfire/firestore'
...
someFunction() {
  const todoRef = db.doc('todos/myTodo')
  const todo$ = docData(todoRef, 'id')
  todo$.subscribe(todo => /* doSomething() */)
}

/* Getting a firestore collection */
import { collectionData } from 'rxfire/firestore'
...
someFunction() {
  const todosRef = db.collection('todos')
  const todos$ = collectionData(todoRef, 'id')
  todos$.subscribe(todos => /* doSomething() */) 
}

                 
/**
 * Preventing memory leaks
 * (make a component instance available for garbage collection)
*/
import { takeUntil } from 'rxjs/operators'
...
destroy$: Subject<boolean> = new Subject<boolean>()
...
componentDidUnload() { // or whatever your unload hook is.
  this.destroy$.next(true)
  this.destroy$.unsubscribe()
}
...
someFunction() {
  const todosRef = db.collection('todos')
  const todos$ = collectionData(todoRef, 'id')
  todos$
    // unsub when destroy$ obs emits
    .pipe(takeUntil(this.destroy$))
    .subscribe(todos => /* doSomething() */)
}