How to check if MKCoordinateRegion contains CLLoca

Question

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 1

Owen Godfrey, the objective-C code doesn´t work, this is the good code: Fails on Objective-C, this is the good code:

/* Standardises and angle to [-180 to 180] degrees */
- (CLLocationDegrees)standardAngle:(CLLocationDegrees)angle {
    angle=fmod(angle,360);
    return angle < -180 ? -360 - angle : angle > 180 ? 360 - 180 : angle;
}

-(BOOL)thisRegion:(MKCoordinateRegion)region containsLocation:(CLLocation *)location{
    CLLocationDegrees deltaLat =fabs([self standardAngle:(region.center.latitude-location.coordinate.latitude)]);
    CLLocationDegrees deltaLong =fabs([self standardAngle:(region.center.longitude-location.coordinate.longitude)]);
    return region.span.latitudeDelta >= deltaLat && region.span.longitudeDelta >=deltaLong;
}
    CLLocationDegrees deltalong = fabs(standardAngle(region.center.longitude - location.coordinate.longitude));
    return region.span.latitudeDelta >= deltaLat && region.span.longitudeDelta >= deltalong;
}

Thanks!

Answer 2

Based on Lukasz solution, but in Swift, in case anybody can make use of Swift:

func isInRegion (region : MKCoordinateRegion, coordinate : CLLocationCoordinate2D) -> Bool {

    let center   = region.center;
    let northWestCorner = CLLocationCoordinate2D(latitude: center.latitude  - (region.span.latitudeDelta  / 2.0), longitude: center.longitude - (region.span.longitudeDelta / 2.0))
    let southEastCorner = CLLocationCoordinate2D(latitude: center.latitude  + (region.span.latitudeDelta  / 2.0), longitude: center.longitude + (region.span.longitudeDelta / 2.0))

    return (
        coordinate.latitude  >= northWestCorner.latitude &&
        coordinate.latitude  <= southEastCorner.latitude &&

        coordinate.longitude >= northWestCorner.longitude &&
        coordinate.longitude <= southEastCorner.longitude
    )
}