ios - How to check if CLCircularRegions intersect -

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i'm developing ios app (with swift) keeps log of user's location history. part of search algorithm, i'd check if 2 clcircularregions intersect, can't seem find core location method or function it. clcircularregion has containscoordinate method, that's not need. know map kit includes functions check intersecting mkmaprects, since i'm not working maps, solutions don't seem ideal.

i hope i'm missing obvious, can't seem figure out. how can check if 2 clcircularregions intersect?

if don't mind small inaccuracies, can assume regions small enough curvature of earth negligible therefore regions can treated planes.

in case, check whether distance of 2 center points smaller sum of radii. 2 circles intersect if , if centers closer sum of radii.

clcircularregion r1, r2;  const double meanearthrad = 6371009; const double metersperdegree = 2 * m_pi * meanearthrad / 360;  double dlat = r2.center.latitude - r1.center.latitude; double dlon = r2.center.longitude - r1.center.longitude;  double actcenterdist = hypot(dlat, dlon) * metersperdegree; double mincenterdist = r1.radius + r2.radius;  if (actcenterdist < mincenterdist) {     // regions intersect }

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