Revisit commit method in FIRWriteBatch (#541)

* revisit FIRWriteBatch commit

*   make commitWithCompletion completion nullable;
*   add commit;
*   add unit test;
*   add swift build test for commit;
*   update CHANGELOG.

1 files changed, 26 insertions, 0 deletions

diff --git a/Firestore/Example/SwiftBuildTest/main.swift b/Firestore/Example/SwiftBuildTest/main.swift
index bea8b56..475c1b2 100644
--- a/Firestore/Example/SwiftBuildTest/main.swift
+++ b/Firestore/Example/SwiftBuildTest/main.swift
@@ -27,6 +27,8 @@ func main() {
 
     writeDocument(at: documentRef);
 
+    writeDocuments(at: documentRef, database: db);
+
     addDocument(to: collectionRef);
 
     readDocument(at: documentRef);
@@ -129,6 +131,30 @@ func writeDocument(at docRef: DocumentReference) {
     }
 }
 
+func writeDocuments(at docRef: DocumentReference, database db: Firestore) {
+  var batch: WriteBatch;
+
+  batch = db.batch();
+  batch.setData(["a" : "b"], forDocument:docRef);
+  batch.setData(["c" : "d"], forDocument:docRef);
+  // commit without completion callback.
+  batch.commit();
+  print("Batch write without completion complete!");
+
+  batch = db.batch();
+  batch.setData(["a" : "b"], forDocument:docRef);
+  batch.setData(["c" : "d"], forDocument:docRef);
+  // commit with completion callback via trailing closure syntax.
+  batch.commit() { error in
+    if let error = error {
+      print("Uh oh! \(error)");
+      return;
+    }
+    print("Batch write callback complete!");
+  }
+  print("Batch write with completion complete!");
+}
+
 func addDocument(to collectionRef: CollectionReference) {
 
     collectionRef.addDocument(data: ["foo": 42]);