Could I set value in CLCircularRegion?

I'm developing app using CLCircularRegion.

I want to set value in CLCircularRegion. So I did region.setValue(forKey:key) but it showed

        if CLLocationManager.locationServicesEnabled() {
            for obj in pushInfoArr! {
                let localLatiStr = obj["local_latit"] as! String
                let localLongitStr = obj["local_longit"] as! String
                let localMsg = obj["local_mesg"] as! String
                let url = obj["cnnct_url"] as! String
                let localLati = Double(localLatiStr)
                let localLongi = Double(localLongitStr)
                let center = CLLocationCoordinate2DMake(localLati!, localLongi!)
                region = CLCircularRegion(center: center, radius: 1000, identifier: localMsg)
                region.setValue(localMsg, forKey: "msg")
                region.setValue(url, forKey: "url")
                region.notifyOnEntry = true
                self.locationManager.startMonitoring(for: region)
            }
    }

"Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key bb"

Could I set value(url) in CLCircularRegion??

Swift isn't Javascript - you can't create new properties on an existing class or struct, and neither CLCircularRegion nor CLRegion from which it inherits has properties msg nor url.

You have misconstrued what setValue does - it is a method on the base class NSObject which allows the setting of an existing property of the class by reference to its "name" or key. Its use is not recommended in Swift (it's an Objective-C legacy).

What you need to do is to create a struct or subclass that holds both your region and your required properties:

Either

struct MyRegion {
    var region: CLCircularRegion
    var msg: String
    var url: String
}

or

class MyRegion: CLCircularRegion {
    var msg: String
    var url: String
    init(centre: CLLocationCoordinate2D, radius: Double, identifier: String, msg: String, url: String) {
        super.init(centre: centre, radius: radius, identifier: identifier)
        self.msg = msg
        self.url = url
    }
}

p.s. don't use 'url' as the name of a property that isn't a URL - call it 'urlString' or some such. I just used that to correspond to your question's terminology.