How to set focus center based on the searched result of geocodeAddressString - street-address

Question

I have only a couple of months experience on Objective-C.
I have a code to search a list of customer address, then show the annotation of these addresses. As the customers cover many regions, I would like to make map view's center and span adapt to the results.
Therefore, I planed to record all searched place marks and calculate an average latitude and longitude. Below is my code
self.mapView.mapType = MKMapTypeStandard;
for (Customer *customer in customers) {
CLGeocoder *geoCoder = [[CLGeocoder alloc] init];
NSString *customerAddress = [Customer getWholeAddressOfCustomer:customer];
NSString *color = #"";
if([customer.status isEqualToString:#"1"])
{
color = #"Green";
}else if ([customer.status isEqualToString:#"2"]) {
color = #"Yellow";
}else if ([customer.status isEqualToString:#"3"])
{
color = #"Red";
}else {
color = customer.status;
}
[geoCoder geocodeAddressString:customerAddress completionHandler:^(NSArray *placemarks, NSError *error)
{
[NSThread sleepForTimeInterval:0.25];
if (placemarks.count == 0)
{
NSLog(#"No place for customer %# was found",customerAddress);
}
CLPlacemark *placemark = [placemarks objectAtIndex:0];
if(placemark.location.coordinate.latitude != 0.000000 && placemark.location.coordinate.longitude != 0.000000)
{
CustomerAnnotation *annotation = [[CustomerAnnotation alloc]initWithCoordinate:placemark.location.coordinate andName:customer.name andNumber:customer.customerNo andColor:color];
[self.mapAnnotations addObject:annotation];
}
}];
}
CLLocationDegrees totalLatitude=0;
CLLocationDegrees totalLongitude = 0;
for (int i=0; i < [self.mapAnnotations count]; i++) {
totalLatitude += [(CustomerAnnotation *)[self.mapAnnotations objectAtIndex:i] coordinate].latitude;
totalLongitude += [(CustomerAnnotation *)[self.mapAnnotations objectAtIndex:i] coordinate].longitude;
[self.mapView addAnnotation:[self.mapAnnotations objectAtIndex:i]];
}
MKCoordinateRegion focusRegion;
focusRegion.center.latitude = totalLatitude/[self.mapAnnotations count];
focusRegion.center.longitude = totalLongitude/[self.mapAnnotations count];
focusRegion.span.latitudeDelta = 20; //will modify this parameter later to self adapt the map
focusRegion.span.longitudeDelta = 20;
[self.mapView setRegion:focusRegion animated:YES];
But the problem is the timing issue like This problem
The setRegion is executed prior to obtaining those place marks. In the solution raised of that link, I should call a method in the completion block. But this solution is not suitable to a multiple address issue as I need to add all place marks to my method before I setRegion.
Is there anyway to make a method be executed after obtaining all results from geocodeAddressString?
Thanks in advance.

Answer 1

Issue resolved.
Outside of the block, I used a counter to record the annotation added.
__block int customerCount = 0;
When this count equals to the whole number, auto focus the central area of all customer.
if (customerCount == [customers count]) {
//Set the focus
}