extension UISplitViewController{
    private struct CustomProperties{
        static var preferredDisplayModeFromString: String = "Automatic"
    }

    var preferredDisplayModeFromString:String {
        get {
            return objc_getAssociatedObject(self, &CustomProperties.preferredDisplayModeFromString) as! String
        }
        set {
            objc_setAssociatedObject(self, &CustomProperties.preferredDisplayModeFromString, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
            switch newValue {
            case "AllVisible":
                self.preferredDisplayMode = .AllVisible
            case "PrimaryHidden":
                self.preferredDisplayMode = .PrimaryHidden
            case "PrimaryOverlay":
                self.preferredDisplayMode = .PrimaryOverlay
            default:
                self.preferredDisplayMode = .Automatic
            }
        }
    }
}