MKOverlayView Fucntions

MKOverlayviewFucntions.m

- (BOOL)canDrawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale {
    NSURL* fileURL = [(HeatMap*)self.overlay localUrlForStyle:@"classic" withMapRect:mapRect andZoomScale:zoomScale];
    if([[NSFileManager defaultManager] fileExistsAtPath:[fileURL path]])
        return YES;
    
    [(HeatMap*)self.overlay fetchFileForStyle:@"classic" withMapRect:mapRect zoomScale:zoomScale completion:^{
        [self setNeedsDisplayInMapRect:mapRect zoomScale:zoomScale];
    }];
    
    return NO;
   
    
}

/**
 * If the above method returns YES, this method performs the actual screen render
 * of a particular tile.
 *
 * You should never perform long processing (HTTP requests, etc.) from this method
 * or else your application UI will become blocked. You should make sure that
 * canDrawMapRect ONLY EVER returns YES if you are positive the tile is ready
 * to be rendered.
 */
- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {
    
    NSURL* fileURL = [(HeatMap*)self.overlay localUrlForStyle:@"classic" withMapRect:mapRect andZoomScale:zoomScale];
    NSData *imageData = [NSData dataWithContentsOfURL:fileURL ];
    if (imageData != nil) {
        UIImage *img = [UIImage imageWithData:imageData];
        
        // Perform the image render on the current UI context
        UIGraphicsPushContext(context);
        [img drawInRect:[self rectForMapRect:mapRect] blendMode:kCGBlendModeNormal alpha:1.0];
        UIGraphicsPopContext();
        
    }

    
}