###Update 13.02.2012:### Added support for cluster different groups of annotations. See the screenshots below.
####How to use: Implement the new OCGrouping protocol on your annotation class, set its grouping-tag and set the clusterByGroupTag property of your OCMapView to true. Take a look at the sample project to see how it works.

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#What is OCMapView? OpenClusterMapView is a simple and easy to use extension of MKMapView for iOS. If you have trouble to display a lot of annotations on the map, this class is for you. OCMapView automatically creates cluster by combinig annotation super fast. It is written in Objective-C + C and works for all iOS applications.

##Screenshots:

#Background: You may already encountered the problem when you adding a several hundred annotations the the MKMapView it will get laggy and everything but user friendly. Many developers believe that iOS can't handle a huge amount of annotations on a MKMapView due the low memory capacities of iDevices. So they start to handle the annotation management themselves with pretty dumb filter methods which won't display all annotations and confuse users even more.

The actual problem is not memory related. It rather occurs because annotationViews are UIViews and these are extremely slow. So if you scroll/zoom a MKMapView with many annotations, iOS has to redraw them all at once and that will take time.

OCMapView combines multiple annotations in a specified range and displays them just as a single annotationView for the whole cluster. So you'll never have too many views which make your app slow and laggy. In addition to that forget to handle the annotations yourself! Just add them all to your OCMapView and it will do everything for you. Even the iPhone 3G with iOS 3.1.x can handle a couple thousand annotations without lagging!

##Set up: OCMapView automatically handles annotations and combines them to clusters for you. Just add the OCMapView folder to your project and you are good to go. Set the class of your MapView in the Interface Builder/Storyboard from MKMapView to OCMapView or create it manually in code like a regular MKMapView. Don't forget to link the MapKit and CoreLocation frameworks to your project and import OCMapView.h into the viewController you are working on.

The sample project is generated with Xcode 4.1 and written for iOS +4.0.

##Usage: Use it just like a regular MKMapView by adding the annotations you want to display and implement the usual MKMapViewDelegate methods.

The MKAnnotationView handling stays completely the same so you can use custom Views for your annotations and clusters. The viewForAnnotation delegate method will return OCAnnotation objects when it generates clusters. So you can provide your custom view:

- (MKAnnotationView *)mapView:(MKMapView *)aMapView viewForAnnotation:(id <MKAnnotation>)annotation{  
    // if it's a cluster  
    if ([annotation isKindOfClass:[OCAnnotation class]]) {  
        // create your custom cluster annotationView here!  
    }  
    // If it's a single annotation  
    else if([annotation isKindOfClass:[Your_Annotation class]]){  
        // create your custom annotationView  as regular here!  
    }  
    return Your_annotationView;  
}

You can customize the behavior of the clusters by setting specific attributes. For more information take a look at the sample project or the documentation.

##OCMapView provides:

• Fast and easy to use class to handle over 9000 annotations on the map at once.
• Very simple installation and usage like the standard MKMapView.
• Easy to upgrade! You can keep all of your MKMapView delegate methods as they are.
• Customize the MKAnnotationViews of generated clusters as of a regular MKAnnotation.
• 2 different clustering algorithms.
• Algorithm help functions are written in C to maximize performance.
• Customize behavior like cluster size.
• Manage clusters yourself by providing an ignore list of annotations.
• NEW: Create independent clusters by using groups.

#Contribute: Apps that use OCMapView:

• official Car2Go App
• cost control for Car2Go aka. aCar2Go
• AbHof
• and a lot of more who do not tell me ;)

If you are using OCMapView and want to contribute, please contact me to add your app to the list of supporting apps!