Helper function to calculate the region needed to show a number of POIs

file.m

// Helper function to calculate the region needed to show a number of POIs
MKCoordinateRegion RegionForAnnotations (NSArray *records)
{
    MKCoordinateRegion region;
    
    // center the map arround our records
    // @see https://devforums.apple.com/message/48525#48525
    double minLatitude = [[records valueForKeyPath:@"@min.latitude"] doubleValue];
    double maxLatitude = [[records valueForKeyPath:@"@max.latitude"] doubleValue];
    
    double minLongitude = [[records valueForKeyPath:@"@min.longitude"] doubleValue];
    double maxLongitude = [[records valueForKeyPath:@"@max.longitude"] doubleValue];
    
    region.center.latitude = (maxLatitude - minLatitude)/2.0 + minLatitude;
    region.center.longitude = (maxLongitude - minLongitude)/2.0 + minLongitude;
    region.span.latitudeDelta = (maxLatitude - minLatitude);
    region.span.longitudeDelta = (maxLongitude - minLongitude);
    
    region.span.latitudeDelta = MAX (region.span.latitudeDelta, 0.03);
    region.span.longitudeDelta = MAX (region.span.longitudeDelta, 0.03);
    
    return region;
}

records must contain objects key value coding-compliant for keys "longitude" and "latitude"