Add a sync method to check a room data source existence

Riot/Modules/MatrixKit/Models/Room/MXKRoomDataSourceManager.h

@@ -78,6 +78,13 @@ typedef enum : NSUInteger {
  */
 - (void)reset;
 
+/**
+ Flag indicating the manager has a room data source for a given room id.
+
+ @param roomId the room id to check.
+ */
+- (BOOL)hasRoomDataSourceForRoom:(NSString*)roomId;
+
 /**
  Get a room data source corresponding to a room id.
  

Riot/Modules/MatrixKit/Models/Room/MXKRoomDataSourceManager.m

@@ -191,6 +191,11 @@ static Class _roomDataSourceClass;
     }
 }
 
+- (BOOL)hasRoomDataSourceForRoom:(NSString *)roomId
+{
+    return roomDataSources[roomId] != nil;
+}
+
 - (void)roomDataSourceForRoom:(NSString *)roomId create:(BOOL)create onComplete:(void (^)(MXKRoomDataSource *roomDataSource))onComplete
 {
     NSParameterAssert(roomId);