@interface FIRMessagingRemoteMessage : NSObject
A remote data message received by the app via FCM (not just the APNs interface).
This is only for devices running iOS 10 or above. To support devices running iOS 9 or below, use the local and remote notifications handlers defined in UIApplicationDelegate protocol.
The downstream message received by the application.
@property (readonly, strong, nonatomic) NSDictionary *_Nonnull appData;