Swift. Why singleton lost data? - swift

Question

Why my data is lost in singleton? Please take a look:
class YtDataManager {
static var shared_instance = YtDataManager()
let apiKey = /*...*/
let /*...*/
var channelData = [NSObject:AnyObject]()
var videosArray = [[NSObject:AnyObject]]()
var playlistId: String { return self.channelData["playlistId"] as! String}
var urlStringForRequestChannelDetails: String { return String("https://www.googleapis.com/youtube/v3/channels?part=contentDetails,snippet&forUsername=\(self./*ChannelName*/)&key=\(self.apiKey)") }
var urlStringForRequestChannelVideos: String { return String("https://www.googleapis.com/youtube/v3/playlistItems?part=snippet&playlistId=\(self.playlistId)&key=\(self.apiKey)") }
func fn1() { /*...*/ }
func fn2() { /*...*/ }
// class definition continue...
Look, from one function(fn1) I'm writing data to channelData:
//...
self.channelData["title"] = snippetDict["title"]
self.channelData["playlistId"] = ((firstItemDict["contentDetails"] as! [NSObject:AnyObject])["relatedPlaylists"] as! [NSObject:AnyObject])["uploads"]
//...
and so on... From second function(fn2), I'm reading data:
//...
let targetURL = NSURL(fileURLWithPath: self.urlStringForRequestChannelVideos)
//...
Hence urlStringForRequestChannelVideos is computational property it uses playlistId (look code above).
Here I was surprised about emptiness of channedData from second function(I saw it in Debug mode, also I printed it's count to stdout outside of function). Why????
class YtFeedViewController: UIViewController {
#IBOutlet weak var menuButton:UIBarButtonItem!
override func viewDidLoad() {
super.viewDidLoad()
if self.revealViewController() != nil {
menuButton.target = self.revealViewController()
menuButton.action = "revealToggle:"
self.view.addGestureRecognizer(self.revealViewController().panGestureRecognizer())
YtDataManager.shared_instance.fn1()
print(YtDataManager.shared_instance.channelData.count) //0
YtDataManager.shared_instance.fn2() //errorness
}
self.navigationItem.title = "YouTube feed"
// Do any additional setup after loading the view.
}