Facebook Friends List in TableView: Think need Async Programming? - facebook

Question

I am trying to get a friend list from Facebook, i have the call request inside the tableview cellforrowatindexpath but i also have it in a separate function too. Thought to try both ways but i get the same result.
If i do a print from inside the completion block i do get results, however, if i try to print friendProfile outside the completion block it returns nil and therefore when i create the table cells they unwrap nil and the code fails. I think it is because the completion block is not returning data until after i call to create the cells. I am reading, and perhaps this has to do with Asynchronous programming? Or needing to wait till data is returned from Facebook? Or will the completion handler always return nil?
`
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var request = FBSDKGraphRequest(graphPath:"/me/taggable_friends", parameters: ["fields":"user_id,first_name,last_name,name,picture.type(large)"]);
request.startWithCompletionHandler ({ (connection : FBSDKGraphRequestConnection!, result : AnyObject!, error : NSError!) -> Void in
if error == nil {
//print("Friends are : \(result)")
let jsonResult = result
self.friendsArray = jsonResult["data"] as! NSArray
var index = 0
for data in self.friendsArray {
let fn = data["first_name"]! as! String
let ln = data["last_name"]! as! String
let id = data["id"]! as! String
let picture = data["picture"] as! NSDictionary
let parsePic = picture["data"] as! NSDictionary
let url = parsePic["url"] as! String
self.friendProfile .updateValue((fn + " " + ln), forKey: id)
self.friendProfilePic .updateValue(url, forKey: id)
self.friendProfileID . updateValue(id, forKey: index)
index++
}
} else {
print("Error Getting Friends \(error)");
}
//if i do a print(friendprofilId) in here it works
})
//but a print(friendprofilId) here returns nil
let cellidentifier = "SettingsTableViewCell"
let cell = tableView.dequeueReusableCellWithIdentifier(cellidentifier, forIndexPath: indexPath) as! SettingsTableViewCell
let id = self.friendProfileID[indexPath.row]
print(self.friendProfileID)
if (id != nil) {
let name = self.friendProfile[id!]
let url = self.friendProfilePic[id!]
// cell.imageView?.image = returnFriendProfileImage(url!)
cell.textLabel!.text = name
}
return cell
}
`

Answer 1

You need to call tableView.reloadData() in the place where you have it commented that it works. Also, don't retrieve your data in cellForRowAtIndexPath. Just call the function you had in viewDidLoad

Answer 2

An asynchronous function call with return immediately, while the completion block will complete once it receives a response from the web server. In your case, you call startWithCompletionHandler, which returns immediately and configure your cell before the completion block receives a response from Facebook's server. It makes sense that friendProfilId is still null since you haven't received the data from Facebook.