Zooming MKMapView to fit annotation pins?

Question

This is the one I found here that worked for me:

(EDIT: I have updated the solution using @Micah's suggestion to increase the pointRect by 0.1 to ensure the rect doesn't end up being infinitesimally small!)

MKMapRect zoomRect = MKMapRectNull;
for (id <MKAnnotation> annotation in mapView.annotations)
{
    MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);
    MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0.1, 0.1);
    zoomRect = MKMapRectUnion(zoomRect, pointRect);
}
[mapView setVisibleMapRect:zoomRect animated:YES];

 

You could also update this to include the userLocation pin by replacing the first line with:

MKMapPoint annotationPoint = MKMapPointForCoordinate(mapView.userLocation.coordinate);
MKMapRect zoomRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0.1, 0.1);

You've got it right.

Find your maximum and minimum latitudes and longitudes, apply some simple arithmetic, and use MKCoordinateRegionMake.

For iOS 7 and above, use showAnnotations:animated:, from MKMapView.h:

// Position the map such that the provided array of annotations are all visible to the fullest extent possible. 
- (void)showAnnotations:(NSArray *)annotations animated:(BOOL)animated NS_AVAILABLE(10_9, 7_0);

Apple has added a new method for IOS 7 to simplify life a bit.

[mapView showAnnotations:yourAnnotationArray animated:YES];

You can easily pull from an array stored in the map view:

yourAnnotationArray = mapView.annotations;

and quickly adjust the camera too!

mapView.camera.altitude *= 1.4;

this won't work unless the user has iOS 7+ or OS X 10.9+ installed. check out custom animation here

I use this this code and works fine for me:

-(void)zoomToFitMapAnnotations:(MKMapView*)aMapView
{
    if([aMapView.annotations count] == 0)
        return;

    CLLocationCoordinate2D topLeftCoord;
    topLeftCoord.latitude = -90;
    topLeftCoord.longitude = 180;

    CLLocationCoordinate2D bottomRightCoord;
    bottomRightCoord.latitude = 90;
    bottomRightCoord.longitude = -180;

    for(MapViewAnnotation *annotation in mapView.annotations)
    {
        topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude);
        topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude);

        bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude);
        bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude);
    }

    MKCoordinateRegion region;
    region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5;
    region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5;
    region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.1; // Add a little extra space on the sides
    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.1; // Add a little extra space on the sides

    region = [aMapView regionThatFits:region];
    [mapView setRegion:region animated:YES];
}

In Swift use

mapView.showAnnotations(annotationArray, animated: true)

In Objective c

[mapView showAnnotations:annotationArray animated:YES];

I have converted the answer by Rafael Moreira. The credit goes to him. For those of you looking for the Swift version, here is the code:

 func zoomToFitMapAnnotations(aMapView: MKMapView) {
    guard aMapView.annotations.count > 0 else {
        return
    }
    var topLeftCoord: CLLocationCoordinate2D = CLLocationCoordinate2D()
    topLeftCoord.latitude = -90
    topLeftCoord.longitude = 180
    var bottomRightCoord: CLLocationCoordinate2D = CLLocationCoordinate2D()
    bottomRightCoord.latitude = 90
    bottomRightCoord.longitude = -180
    for annotation: MKAnnotation in myMap.annotations as! [MKAnnotation]{
        topLeftCoord.longitude = fmin(topLeftCoord.longitude, annotation.coordinate.longitude)
        topLeftCoord.latitude = fmax(topLeftCoord.latitude, annotation.coordinate.latitude)
        bottomRightCoord.longitude = fmax(bottomRightCoord.longitude, annotation.coordinate.longitude)
        bottomRightCoord.latitude = fmin(bottomRightCoord.latitude, annotation.coordinate.latitude)
    }

    var region: MKCoordinateRegion = MKCoordinateRegion()
    region.center.latitude = topLeftCoord.latitude - (topLeftCoord.latitude - bottomRightCoord.latitude) * 0.5
    region.center.longitude = topLeftCoord.longitude + (bottomRightCoord.longitude - topLeftCoord.longitude) * 0.5
    region.span.latitudeDelta = fabs(topLeftCoord.latitude - bottomRightCoord.latitude) * 1.4
    region.span.longitudeDelta = fabs(bottomRightCoord.longitude - topLeftCoord.longitude) * 1.4
    region = aMapView.regionThatFits(region)
    myMap.setRegion(region, animated: true)
}