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POOptimization for MKAnnotations and Core Data
 

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  1. POOptimization for MKAnnotations and Core Data
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    <p>I have some locations ( in this case >3000 ) stored with Core Data. Once I open the map, I fetch the locations and store them in an array. Each time the mapview region is changed I call a function which will calculate which annotations are visible in the current <code>visibleMaprect</code> and filter them by pixel-distance. ( I know there would be more complex optimizations, like quadtrees, but I would not really implement it right now, if it's not extremely necessary ). This is my code : </p> <pre><code>//locations is an array of NSManagedObjects for (int i =0 ; i &lt; [locations count]; i++) { // managed object class for faster access, valueforkey takes ages ... LocationEntity * thisLocation = [locations objectAtIndex:i]; CLLocationCoordinate2D coord = CLLocationCoordinate2DMake( [thisLocation.latitude doubleValue], [thisLocation.longitude doubleValue]) ; // mapRect is mapView.visibleMapRect BOOL isOnScreen = MKMapRectContainsPoint(mapRect, MKMapPointForCoordinate(coord)); if (isOnScreen) { CGPoint cgp = [mapView convertCoordinate:coord toPointToView:mapView]; // compare the distance to already existing annotations for (int idx = 0; idx &lt; [annotations count] &amp;&amp; hasEnoughDistance; idx++) { CGPoint cgp_prev = [mapView convertCoordinate:[[annotations objectAtIndex:idx] coordinate] toPointToView:mapView]; if ( getDist(cgp, cgp_prev) &lt; dist ) hasEnoughDistance = FALSE; } } if (hasEnoughDistance) // if it's ok, create the annotation, add to an array and after the for add all to the map } </code></pre> <p>The map is freezing for a few seconds after each zoom/movement. I checked with time profiler and the simple obtainment of coordinates is taking sometimes 1 whole second, sometimes just 0.1, even though the coordinates are indexed attributes in my model... Also these type of lines seem to take ages : <code>CGPoint cgp = [mapView convertCoordinate:coord toPointToView:mapView];</code> </p> <p>Any suggestions how could I calculate the pixel/point distance between two annotations/coordinates without going through this function ? Or any optimization suggestions for Core Data? </p> <p>Thanks :)</p>
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