add show

src/app/services/db.service.ts

@@ -0,0 +1,44 @@
+import {Injectable} from '@angular/core';
+import {AngularFirestore, AngularFirestoreCollection, AngularFirestoreDocument} from '@angular/fire/firestore';
+import {Observable} from 'rxjs';
+import {map} from 'rxjs/operators';
+
+type CollectionPredicate<T> = string | AngularFirestoreCollection<T>;
+type DocumentPredicate<T> = string | AngularFirestoreDocument<T>;
+
+@Injectable({
+  providedIn: 'root'
+})
+export class DbService {
+
+  constructor(private afs: AngularFirestore) {
+  }
+
+  public col<T>(ref: CollectionPredicate<T>, queryFn?): AngularFirestoreCollection<T> {
+    return typeof ref === 'string' ? this.afs.collection<T>(ref, queryFn) : ref;
+  }
+
+  public doc<T>(ref: DocumentPredicate<T>): AngularFirestoreDocument<T> {
+    return typeof ref === 'string' ? this.afs.doc<T>(ref) : ref;
+  }
+
+  public doc$<T>(ref: DocumentPredicate<T>): Observable<T> {
+    return this.doc(ref).snapshotChanges().pipe(
+      map(doc => {
+        const data = doc.payload.data();
+        const id = doc.payload.id;
+        return {...data, id} as T;
+      })
+    );
+  }
+
+  public col$<T>(ref: CollectionPredicate<T>, queryFn?): Observable<T[]> {
+    return this.col(ref, queryFn).snapshotChanges().pipe(
+      map(doc => doc.map(_ => {
+        const data = _.payload.doc.data();
+        const id = _.payload.doc.id;
+        return {...data, id} as T;
+      }))
+    );
+  }
+}