Lukasz Lukasz - 2 months ago 17
iOS Question

How to check if MKCoordinateRegion contains CLLocationCoordinate2D without using MKMapView?

I need to check if user location belongs to the MKCoordinateRegion.
I was surprised not to find simple function for this, something like: CGRectContainsCGPoint(rect, point).

I found following piece of code:

CLLocationCoordinate2D topLeftCoordinate =
CLLocationCoordinate2DMake(region.center.latitude
+ (region.span.latitudeDelta/2.0),
region.center.longitude
- (region.span.longitudeDelta/2.0));


CLLocationCoordinate2D bottomRightCoordinate =
CLLocationCoordinate2DMake(region.center.latitude
- (region.span.latitudeDelta/2.0),
region.center.longitude
+ (region.span.longitudeDelta/2.0));

if (location.latitude < topLeftCoordinate.latitude || location.latitude > bottomRightCoordinate.latitude || location.longitude < bottomRightCoordinate.longitude || location.longitude > bottomRightCoordinate.longitude) {

// Coordinate fits into the region

}


But, I am not sure if it is accurate as documentation does not specify exactly how the region rectangle is calculated.

There must be simpler way to do it. Have I overlooked some function in the MapKit framework documentation?

Answer

In case there is anybody else confused with latitudes and longitues, here is tested, working solution:

MKCoordinateRegion region = self.mapView.region;

CLLocationCoordinate2D location = user.gpsposition.coordinate;
CLLocationCoordinate2D center   = region.center;
CLLocationCoordinate2D northWestCorner, southEastCorner;

northWestCorner.latitude  = center.latitude  - (region.span.latitudeDelta  / 2.0);
northWestCorner.longitude = center.longitude - (region.span.longitudeDelta / 2.0);
southEastCorner.latitude  = center.latitude  + (region.span.latitudeDelta  / 2.0);
southEastCorner.longitude = center.longitude + (region.span.longitudeDelta / 2.0);

if (
    location.latitude  >= northWestCorner.latitude && 
    location.latitude  <= southEastCorner.latitude &&

    location.longitude >= northWestCorner.longitude && 
    location.longitude <= southEastCorner.longitude
    )
{
    // User location (location) in the region - OK :-)
    NSLog(@"Center (%f, %f) span (%f, %f) user: (%f, %f)| IN!", region.center.latitude, region.center.longitude, region.span.latitudeDelta, region.span.longitudeDelta, location.latitude, location.longitude);

}else {

    // User location (location) out of the region - NOT ok :-(
    NSLog(@"Center (%f, %f) span (%f, %f) user: (%f, %f)| OUT!", region.center.latitude, region.center.longitude, region.span.latitudeDelta, region.span.longitudeDelta, location.latitude, location.longitude);
}