refs #492: post errors with background tile fetch problems

@@ -105,6 +105,12 @@ typedef enum : short {
 *   @param totalTileCount The total number of of tiles required for coverage of the desired geographic area. */
 - (void)tileCache:(RMTileCache *)tileCache didBackgroundCacheTile:(RMTile)tile withIndex:(NSUInteger)tileIndex ofTotalTileCount:(NSUInteger)totalTileCount;
 
+/** Sent upon error when trying to cache a tile in a background cache operation. 
+*   @param tileCache The tile cache.
+*   @param error The error received.
+*   @param tile A structure representing the tile in question. */
+- (void)tileCache:(RMTileCache *)tileCache didReceiveError:(NSError *)error whenCachingTile:(RMTile)tile;
+
 /** Sent when all tiles have completed downloading and caching. 
 *   @param tileCache The tile cache. */
 - (void)tileCacheDidFinishBackgroundCache:(RMTileCache *)tileCache;

@@ -406,6 +406,15 @@
                             });
                         }
                     }
+                    else
+                    {
+                        if ([_backgroundCacheDelegate respondsToSelector:@selector(tileCache:didReceiveError:whenCachingTile:)])
+                        {
+                            [_backgroundCacheDelegate tileCache:weakSelf
+                                                didReceiveError:internalOperation.error
+                                                whenCachingTile:RMTileMake((uint32_t)x, (uint32_t)y, zoom)];
+                        }
+                    }
                 }];
 
                 [_backgroundFetchQueue addOperation:operation];

@@ -35,4 +35,6 @@
 
 - (id)initWithTile:(RMTile)tile forTileSource:(id <RMTileSource>)source usingCache:(RMTileCache *)cache;
 
+@property (nonatomic, strong) NSError *error;
+
 @end

@@ -73,6 +73,17 @@
 
         if ( ! data || error != nil)
         {
+            if (error != nil)
+            {
+                self.error = error;
+            }
+            else
+            {
+                self.error = [NSError errorWithDomain:NSURLErrorDomain
+                                                 code:NSURLErrorUnknown
+                                             userInfo:nil];
+            }
+
             [self cancel];
         }
         else