Variable captured by closure before being initialized

Question

I'm trying to store the number of results from a query into an integer so that I can use it to determine the number of rows in a table. However, I'm getting the following error: Variable 'numberOfGames' captured by a closure before being initialized' on the line query.findObjectsInBackgroundWithBlock{.

I also get another error Variable 'numberOfGames' used before being initialized on the line return numberOfGames.

Here's the function that contains the two errors:

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
    {
        var user: PFUser!

        var numberOfGames: Int

        //...query code....removed to make it easier to read

        var query = PFQuery.orQueryWithSubqueries([userQuery, userQuery2, currentUserQuery, currentUserQuery2])
        query.findObjectsInBackgroundWithBlock{
            (results: [AnyObject]?, error: NSError?) -> Void in

            if error != nil {
                println(error)
            }

            if error == nil{

                if results != nil{
                    println(results)
                    numberOfGames = results!.count as Int
                }
            }
        }
        return numberOfGames
    }

Solution

You need to initialize the variable before use it inside a closure:

As per apple documentation

If you use a closure to initialize a property, remember that the rest of the instance has not yet been initialized at the point that the closure is executed. This means that you cannot access any other property values from within your closure, even if those properties have default values. You also cannot use the implicit self property, or call any of the instance’s methods.

The command var numberOfGames: Int just declare it to initialize you can use var numberOfGames = Int() or var numberOfGames:Int = 0

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
    {
        var user: PFUser!
        var numberOfGames:Int = 0
        var query = PFQuery.orQueryWithSubqueries([userQuery, userQuery2, currentUserQuery, currentUserQuery2])
        query.findObjectsInBackgroundWithBlock{
            (results: [AnyObject]?, error: NSError?) -> Void in
            if error != nil {
                println(error)
            }
            if error == nil{
                if results != nil{
                    println(results)
                    numberOfGames = results!.count as Int
                }
            }
        }
        return numberOfGames
    }

Comments

[winston]

*facepalm ... I need to learn the difference between declare and initializing. Thank you for the help!

[ScottyBlades]

@Anton, Wouldn't the alternative be to let the program intermittently crash at runtime without prior warning, via attempting to access a memory address without a value?

[Anton Tropashko]

Somehow it was all working elegantly and without million pitfalls in objc day and age predating the design-by-committee of swift