Use sets for regions in didRangeBeacons

RangeWhileMonitorPart05.swift

    func locationManager(manager: CLLocationManager!, didRangeBeacons beacons: [AnyObject]!, inRegion region: CLBeaconRegion!) {
        var latestRegions = Set<CLBeaconRegion>()
        
        // Create CLBeaconRegions from CLBeacons
        if let beacons = beacons as? [CLBeacon] {
            for beacon in beacons {
                latestRegions.insert(regionFromBeacon(beacon))
            }
        }
        
        let enteredRegions = latestRegions.subtract(currentRegions)
        let exitedRegions = currentRegions.subtract(latestRegions)
        currentRegions = latestRegions
        
        if enteredRegions.count > 0 {
            println("Entered")
            println(enteredRegions)
        }
        
        if exitedRegions.count > 0 {
            println("Exited")
            println(exitedRegions)
        }
    }

    func regionFromBeacon(beacon: CLBeacon) -> CLBeaconRegion {
        let major = CLBeaconMajorValue(beacon.major.integerValue)
        let minor = CLBeaconMinorValue(beacon.minor.integerValue)
        let identifier = "\(beacon.proximityUUID.UUIDString).\(major).\(minor)" // Used for "is equal" check in Sets
        return CLBeaconRegion(proximityUUID: beacon.proximityUUID, major: major, minor: minor, identifier: identifier)
    }