Ich versuche zu beobachtencollectionView.contentSize so was

func startObserveCollectionView() {
    collectionView.addObserver(self, forKeyPath: "contentSize", options: NSKeyValueObservingOptions.Old.union(NSKeyValueObservingOptions.New), context: &SearchDasboardLabelContext)
}

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    if context == &SearchDasboardLabelContext {       
        if object === collectionView && keyPath! == "contentSize" {
            print(change)               
        }
    }
}

und im xcode terminal habe ich einNSSize notCGSize so was

Optional(["old": NSSize: {320, 0}, "new": NSSize: {375, 39.5}, "kind": 1])

In Ziel-C habe ich MethodeCGSizeValue

CGSize newContentSize = [[change objectForKey:NSKeyValueChangeNewKey] CGSizeValue];

Gibt es eine Methode wieCGSizeValue in swift

Ich habe in swift @ versucvar newContentSize = change[NSKeyValueChangeNewKey]?.CGSizeValue() aber habe Fehler

could not find member 'CGSizeValue'

not jemandem helfen? Vielen Dan