Cannot assign value of type '()' to type '[customObject]' - while in a completion handler

Question

I'm trying to reload a collection view after the json data has been updated but am running into the error:

Cannot assign value of type '()' to type '[ChannelInfo]'

This is how I have the custom object 'ChannelInfo' setup:

class ChannelInfo: NSObject {

  var logo: String?
  var channelName: String?
  var id: NSNumber?


  init(logo: String, channelName: String , id: NSNumber) {

    self.logo = logo
    self.channelName = channelName
    self.id = id
  }

  init(resDictionary: [String:Any]) {

    logo = resDictionary["artwork_608x342"] as? String
    channelName = resDictionary["name"] as? String
    id = resDictionary["id"] as? NSNumber

  }


  static func updateAllChannels(completionHandler:@escaping (_ channels: [ChannelInfo]) -> Void){

    let nm = NetworkManager.sharedManager// singleton handles network connections and json parsing


    nm.getJSONData(urlExtension: "channels/all/0/50", completion: {
      data in

      var channels = [ChannelInfo]()

      if let jsonDictionary = nm.parseJSONFromData(data)
      {
        let resultsDictionaries = jsonDictionary["results"] as! [[String : Any]]
        for resultsDictionary in resultsDictionaries {// enumerate through dictionary
          let newChannel = ChannelInfo(resDictionary: resultsDictionary)
          channels.append(newChannel)
        }
      }
      completionHandler(channels)

    })
  }
}

This is how I reload the collection view after the json objects have been updated:

 var channelArray: [ChannelInfo] = []

      override func viewDidLoad() {

        channelArray = ChannelInfo.updateAllChannels(completionHandler: { _ in

        self.channelCollectionView.reloadData()
        })//Error happens here starting with 'channelArray'
    }

I get the feeling I may be missing a step, any help is appreciated.

Answer 1

Okay, let's take this one step at a time. You are saying

ChannelInfo.updateAllChannels...

So let's look at how that updateAllChannels method is declared:

static func updateAllChannels(
    completionHandler:@escaping (_ channels: [ChannelInfo]) -> Void){

So this a static function that returns no result .

But what you are actually saying is:

channelArray = ChannelInfo.updateAllChannels...

But we have just established that updateAllChannels returns no result . So there is nothing there for you to assign to channelArray . The whole notion of assignment here makes no sense. And the compiler is telling you so. You can't have this assignment channelArray = . Delete that part.

---

I think (but don't quote me) that your larger problem is that you are ignoring the value returned to the completion handler. You have this:

ChannelInfo.updateAllChannels(completionHandler: { _ in
    self.channelCollectionView.reloadData()
})

See the _ in at the end of the first line? I think that's your whole issue. updateAllChannels is handing you back the channels as the parameter and you are throwing them away . Instead, I think you want something like this:

ChannelInfo.updateAllChannels(completionHandler: { channels in
    channelArray = channels
    self.channelCollectionView.reloadData()
})