Custom pin with alphanumeric representation in MapKit - ios

Question

I am now at a point of teaching myself the use of MapKit in Objective C. I got to the point where I can autozoom to a location that contains several annotations. I represent the annotations with the built in pins. If you click on the pin I have a an alphanumeric 2 character string to represent that spot.
I thought to myself, for better usability, why not replace the pins with the actual data. Kind of like a weathermap where they show the temperature as a pin. Is this doable?
I researched this and all I could find is this:
- (MKAnnotationView *)mapView:(MKMapView *)map viewForAnnotation:(id <MKAnnotation>)annotation
{
static NSString *AnnotationViewID = #"annotationViewID";
MKAnnotationView *annotationView = (MKAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationViewID];
if (annotationView == nil) {
annotationView = [[[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:AnnotationViewID] autorelease];
}
annotationView.image = [UIImage imageNamed:#"location.png"];
annotationView.annotation = annotation;
return annotationView;
}
The problem is that I cannot and should not have to have a custom image for each combination of the two characters. Is there a way for me to draw these numbers at the location of the pin.
I found this reference:
https://developer.apple.com/library/ios/documentation/userexperience/conceptual/LocationAwarenessPG/AnnotatingMaps/AnnotatingMaps.html
Am I on the right track. Are there some full examples I can leverage to better understand the flow.
I want to be able to select that custom pin however and segue or show more details.
Thank you for your time.

Answer 1

Anna, thank you for the link, I tried it and it worked. I made some changes to improve the esthetic of the label and I thought I would post my findings here for reference:
-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id)annotation {
if ([annotation isKindOfClass:[MKUserLocation class]])
return nil;
static NSString *reuseId = #"MapViewController";
MKAnnotationView *av = [mapView dequeueReusableAnnotationViewWithIdentifier:reuseId];
if (av == nil)
{
av = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:reuseId];
UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 20)];
//UILabel *lbl = [[UILabel alloc] init];;
lbl.backgroundColor = [UIColor clearColor]; // This makes the background clear and just shows the text
lbl.textColor = [UIColor whiteColor]; // Use any colour you wish
lbl.alpha = 1.0; //0.5;
lbl.tag = 42;
lbl.font = [UIFont fontWithName:#"Helvetica-Bold" size:16.0]; // This is optional, I found this fond and size most readable
[av addSubview:lbl];
//Following lets the callout still work if you tap on the label...
av.canShowCallout = YES;
av.frame = lbl.frame;
} else {
av.annotation = annotation;
}
UILabel *lbl = (UILabel *)[av viewWithTag:42];
// I added this to the text to improve its visibility by essentially adding a stroke around the text. Well its a poor man's stroke by adding a shadow
lbl.layer.shadowColor = [[UIColor blackColor] CGColor];
lbl.layer.shadowOffset = CGSizeMake(0.0f, 0.0f);
lbl.layer.shadowOpacity = 1.0f;
lbl.layer.shadowRadius = 1.0f;
lbl.text = annotation.title;
return av;
}