Nested closures does not like argument list

Question

A UIView needs to change a warning label depending on the completion handler of a custom control:

    voucherInputView.completionHandler = {[weak self] (succ         


        

Answer 1

The problem is that the closure is implicitly returning the result of this expression:

self?.warningLabel.alpha = 1.0

but the closure itself is declared as returning Void.

Adding an explicit return should resolve the problem:

UIView.animateWithDuration(NSTimeInterval(1.0), animations: { ()-> Void in
    self?.warningLabel.alpha = 1.0
    return
})

Answer 2

Antonio's solution also applies with nested closures, like doing an AFNetworking request within UITableViewRowAction handler.

override func tableView(tableView: UITableView, editActionsForRowAtIndexPath indexPath: NSIndexPath) -> [AnyObject]? {

    let cleanRowAction = UITableViewRowAction(style: UITableViewRowActionStyle.Default, title: "Do Stuff", handler: {[weak self](action: UITableViewRowAction!, indexPath: NSIndexPath!) in

        AFHTTPSessionManager(baseURL: NSURL(string: "http://baseurl")).PUT("/api/", parameters: nil, success: { (task: NSURLSessionDataTask!, response: AnyObject!) -> Void in

                // Handle success

                self?.endEditing()
                return
            }, failure: { (task: NSURLSessionDataTask!, error: NSError!) -> Void in

                // Handle error

                self?.endEditing()
                return
        })
        return

    })

    cleanRowAction.backgroundColor = UIColor.greenColor()
    return [cleanRowAction]
}