feat(firestore): add samples for sum and average

Author: Lyokone

packages/firebase_snippets_app/lib/snippets/firestore.dart

@@ -823,25 +823,18 @@ class FirestoreSnippets extends DocSnippet {
 
   void filterQuery_or() {
     // [START firestore_query_filter_or]
-    var query = db.collection("cities")
-      .where(
-        Filter.or(
-          Filter("capital", isEqualTo: true),
-          Filter("population", isGreaterThan: 1000000)
-        ));
+    var query = db.collection("cities").where(Filter.or(
+        Filter("capital", isEqualTo: true),
+        Filter("population", isGreaterThan: 1000000)));
     // [END firestore_query_filter_or]
   }
 
   void filterQuery_or2() {
     // [START firestore_query_filter_or_compound]
-    var query = db.collection("cities")
-      .where(
-        Filter.and(
-          Filter("state", isEqualTo: "CA"),
-        Filter.or(
-          Filter("capital", isEqualTo: true),
-          Filter("population", isGreaterThan: 1000000)
-        )));
+    var query = db.collection("cities").where(Filter.and(
+        Filter("state", isEqualTo: "CA"),
+        Filter.or(Filter("capital", isEqualTo: true),
+            Filter("population", isGreaterThan: 1000000))));
     // [END firestore_query_filter_or_compound]
   }
 
@@ -865,6 +858,52 @@ class FirestoreSnippets extends DocSnippet {
     // [END count_aggregate_query]
   }
 
+  void aggregationQuery_sum() {
+    // [START sum_aggregate_collection]
+    db.collection("users").aggregate(sum("age")).get().then(
+          (res) => print(res.getAverage("age")),
+          onError: (e) => print("Error completing: $e"),
+        );
+    // [END sum_aggregate_collection]
+  }
+
+  void aggregationQuery_sum2() {
+    // [START sum_aggregate_query]
+    db
+        .collection("users")
+        .where("age", isGreaterThan: 10)
+        .aggregate(sum("age"))
+        .get()
+        .then(
+          (res) => print(res.getAverage("age")),
+          onError: (e) => print("Error completing: $e"),
+        );
+    // [END sum_aggregate_query]
+  }
+
+  void aggregationQuery_average() {
+    // [START average_aggregate_collection]
+    db.collection("users").aggregate(average("age")).get().then(
+          (res) => print(res.getAverage("age")),
+          onError: (e) => print("Error completing: $e"),
+        );
+    // [END average_aggregate_collection]
+  }
+
+  void aggregationQuery_average2() {
+    // [START average_aggregate_query]
+    db
+        .collection("users")
+        .where("age", isGreaterThan: 10)
+        .aggregate(average("age"))
+        .get()
+        .then(
+          (res) => print(res.getAverage("age")),
+          onError: (e) => print("Error completing: $e"),
+        );
+    // [END average_aggregate_query]
+  }
+
   void orderAndLimitData_orderAndLimitData() {
     // [START order_and_limit_data_order_and_limit_data]
     final citiesRef = db.collection("cities");
@@ -951,7 +990,8 @@ class FirestoreSnippets extends DocSnippet {
         final next = db
             .collection("cities")
             .orderBy("population")
-            .startAfterDocument(lastVisible).limit(25);
+            .startAfterDocument(lastVisible)
+            .limit(25);
 
         // Use the query for pagination
         // ...