swift function not returning string?

Question

I created a function to return a username with a Firebase query on the userID parameter. I want to use this username to populate the text labels in a tableView. Although the query within the function returns the correct value, the value does not seem to be returned:

func getUser(userID: String) -> String {

        var full_name: String = ""
        rootRef.child("users").child(userID).observeSingleEventOfType(.Value, withBlock: { (snapshot) in
            // Get user value
            let first_name = snapshot.value!["first_name"] as! String
            let last_name = snapshot.value!["last_name"] as! String
            full_name = first_name + " " + last_name
            print(full_name) // returns correct value
        })
        return full_name //printing outside here just prints a blank space in console
    }

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath)

        let inviteDict = invites[indexPath.row].value as! [String : AnyObject]
        if let userID = inviteDict["invitedBy"] as? String {

            let name = getUser(userID)

            cell.textLabel!.text = name
        }
        return cell
    }
}

The cells don't have text. Printing the function return to console just prints blank space. Any ideas as to what's wrong?

Thanks!

Reinier Melian · Accepted Answer · 2016-06-20 22:56:00Z

1

Your problem is that your getUser function executes an block to get the full_name value, but you are returning on another thread, so when this line return full_name executes, is almost impossible that your block has ended so your function returns "" instead of your desired value

try this instead

func getUser(userID: String,closure:((String) -> Void)?) -> Void {

        var full_name: String = ""
        rootRef.child("users").child(userID).observeSingleEventOfType(.Value, withBlock: { (snapshot) in
            // Get user value
            let first_name = snapshot.value!["first_name"] as! String
            let last_name = snapshot.value!["last_name"] as! String
            full_name = first_name + " " + last_name
            print(full_name) // returns correct value
            closure(full_name)
        })
    }

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath)

        let inviteDict = invites[indexPath.row].value as! [String : AnyObject]
        if let userID = inviteDict["invitedBy"] as? String {

            let name = getUser(userID, closure: { (name) in
                cell.textLabel!.text = name
            })
        }
        return cell
    }

I hope this helps you, PS I am not sure if this works because i don't have this library

edited Jun 20, 2016 at 22:56

answered Jun 20, 2016 at 22:30

Reinier Melian

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1 Comment

winston Over a year ago

That worked! So...why did your solution work? What is a "closure"? Thank you so much!!

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