Search array of locations within a radius

nsarrayradius.m

// NSArray *locations as an array of CLLocation* that you wish to filter
// with a given radius constant.
CLLocationDistance radius = kSomeRadius;

// Target you want to test against to see if it is within the radius bounds.
CLLocation* target = [[CLLocation alloc] initWithLatitude:someLat longitude:someLon];

NSArray *locationsWithinRadius = [locations objectsAtIndexes:
                                 [locations indexesOfObjectsPassingTest:
                                  ^BOOL(id obj, NSUInteger idx, BOOL *stop) {
                                      return [(CLLocation*)obj distanceFromLocation:target] < radius;
                                  }]];
                                  
// Return locationsWithinRadius.