Firestore project: Import of API interfaces. (#1337)

- 198063502 Address comment upstream. by zxu <zxu>
  - 197942352 Fix style upstream and fix destination depot in copybara. by zxu <zxu>
  - 197925542 Fix headers with change from GitHub, see the current diff... by zxu <zxu>
  - 197922012 Implement ListenerRegistration::Remove(). by zxu <zxu>
  - 197713382 Implement more on listener class and implement ListenerRe... by zxu <zxu>
  - 196551381 Implement more on listener class and implement the Docume... by zxu <zxu>
  - 196276752 Implement the SnapshotMetadata with inline methods and (n... by zxu <zxu>
  - 195841793 Implement the wrapper class for callback (EventListener). by zxu <zxu>
  - 194112388 Add Android-Wrapper for DocumentReference's non-callback ... by zxu <zxu>
  - 192445183 Add Android-Wrapper for Firestore's remaining methods. by zxu <zxu>
  - 190986604 Manually import the public portion of by mcg <mcg>
  - 189013767 Add Android-Wrapper for Firestore's method that does not ... by zxu <zxu>
  - 188809445 Import of firebase-ios-sdk from Github. by mcg <mcg>
  - 187049498 Import of firebase-ios-sdk from Github. by mcg <mcg>
  - 184568931 Import of firebase-ios-sdk from Github. by mcg <mcg>

ORIGINAL_AUTHOR=Firebase <firebase-noreply>
PiperOrigin-RevId: 198063502

1 files changed, 5 insertions, 5 deletions

diff --git a/Firestore/core/include/firebase/firestore/event_listener.h b/Firestore/core/include/firebase/firestore/event_listener.h
index 6c94428..cbe8a28 100644
--- a/Firestore/core/include/firebase/firestore/event_listener.h
+++ b/Firestore/core/include/firebase/firestore/event_listener.h
@@ -22,19 +22,19 @@
 #ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_EVENT_LISTENER_H_
 #define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_EVENT_LISTENER_H_
 
+#include "firebase/firestore/firestore_errors.h"
+
 namespace firebase {
 namespace firestore {
 
-// TODO(rsgowman): replace these forward decl's with appropriate includes (once
-// they exist)
-class Error;
-
 /**
  * @brief An interface for event listeners.
  */
 template <typename T>
 class EventListener {
  public:
+  virtual ~EventListener() {
+  }
   /**
    * @brief OnEvent will be called with the new value or the error if an error
    * occurred.
@@ -44,7 +44,7 @@ class EventListener {
    * @param value The value of the event. null if there was an error.
    * @param error The error if there was error. null otherwise.
    */
-  void OnEvent(const T* value, const Error* error);
+  virtual void OnEvent(const T* value, const Error* error) = 0;
 };
 
 }  // namespace firestore