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    <p>I guess what you're looking for is :</p> <pre><code>- (NSSet *)annotationsInMapRect:(MKMapRect)mapRect </code></pre> <p>Quoting <a href="http://developer.apple.com/library/ios/documentation/MapKit/Reference/MKMapView_Class/MKMapView/MKMapView.html#//apple_ref/occ/instm/MKMapView/annotationsInMapRect%3a" rel="nofollow">Apple documentation</a> :</p> <blockquote> <p>This method offers a fast way to retrieve the annotation objects in a particular portion of the map. This method is much faster than doing a linear search of the objects in the annotations property yourself.</p> </blockquote> <p>Take care that's it's only <em>Available in iOS 4.2 and later</em>, I'm afraid there is no other solution than custom code in previous iOS versions.</p> <p><strong>EDIT</strong> About your comment : My guess is that for a few thousands annotation, the above method <em>should</em> do the trick, <code>MKAnnotation</code> is a lightweight protocol, scanning an array by filtering on coordinate should be ok. But beware on not adding thousands of <code>MKAnnotationView</code>, that works on an iPhone 4, already did it, but you almost can't scroll map :)</p> <p>Then I would suggest :</p> <ol> <li>Use that method, quick to code, easy, then do some performance tests, <em>on device</em></li> <li>If performances are not enough.... or you have to support prevous iOS versios, no magic, write you own code. (shouldn't be that hard, there are utility methods for converting regions and such)</li> </ol> <p>About memory, hey, these devices have easily at least 64MB free memory for your app, and will kill some processes if not, don't be scared by a few K of annotations! Just take care of memory leaks, especially on such intensive processes.</p>
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    1. POiOS SDK - Displaying # most important POIs at any displayed map range
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    1. USVincent Guerci
    1. USVincent Guerci
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    1. COThanks. To use `annotationsInMapRect`, I have to annotate all POIs (could be some k), and through `regionDidChangeAnimated` create/update the annotation views for the ones I'm interested in. My annotation class is pretty lightweight (1x NSString and a pointer to my object), but when we are talking for thousands of them, do you think this approach is efficient? It's actually a question of choosing: (memory usage) load all and display needed VS (speed impact) traverse all and annotate needed (The server backend is still premature so I can't test with big amount of data.)
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      1. USAlexandros Chalatsis
    2. COedited answer about your comment. If server doesn't provide enough data, just generate random test data by code!
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      1. USVincent Guerci
 

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