Swift Thread1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) - ios

Question

There is a SS of error
This happened after add refresh method in to viewDidLoad for pull to refresh . Im using parse.com and that followers table is empty.
I found some questions about some error. But i didn't found anything same as my question or maybe i don't understand.
How can i fix this what is the problem ?
import UIKit
import Parse
class TableViewController: UITableViewController {
var usernames = [""]
var userids = [""]
var isFollowing = ["":false]
var refresher: UIRefreshControl!
func refresh() {
var query = PFUser.query()
query?.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if let users = objects {
self.usernames.removeAll(keepCapacity: true)
self.userids.removeAll(keepCapacity: true)
self.isFollowing.removeAll(keepCapacity: true)
for object in users {
if let user = object as? PFUser {
if user.objectId! != PFUser.currentUser()?.objectId {
self.usernames.append(user.username!)
self.userids.append(user.objectId!)
var query = PFQuery(className: "followers")
query.whereKey("follower", equalTo: (PFUser.currentUser()?.objectId)!)
query.whereKey("following", equalTo: user.objectId!)
query.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if let objects = objects {
if objects.count > 0 {
self.isFollowing[user.objectId!] = true
} else {
self.isFollowing[user.objectId!] = false
}
}
if self.isFollowing.count == self.usernames.count {
self.tableView.reloadData()
self.refresher.endRefreshing()
}
})
}
}
}
}
})
}
override func viewDidLoad() {
super.viewDidLoad()
refresher = UIRefreshControl()
refresher.attributedTitle = NSAttributedString(string: "Pull to refresher")
refresher.addTarget(self , action: "refresh" , forControlEvents: UIControlEvents.ValueChanged)
self.tableView.addSubview(refresher)
refresh()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
return usernames.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as! UITableViewCell
cell.textLabel?.text = usernames[indexPath.row]
let followedOnjectId = userids[indexPath.row]
if isFollowing[followedOnjectId] == true {
cell.accessoryType = UITableViewCellAccessoryType.Checkmark
}
return cell
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
var cell:UITableViewCell = tableView.cellForRowAtIndexPath(indexPath)!
let followedOnjectId = userids[indexPath.row]
if isFollowing[followedOnjectId] == false{
isFollowing[followedOnjectId] = true
cell.accessoryType = UITableViewCellAccessoryType.Checkmark
var following = PFObject(className: "followers")
following["following"] = userids[indexPath.row]
following["follower"] = PFUser.currentUser()?.objectId
following.saveInBackground()
}else
{
isFollowing[followedOnjectId] = false
cell.accessoryType = UITableViewCellAccessoryType.None
var query = PFQuery(className: "followers")
query.whereKey("follower", equalTo: PFUser.currentUser()!.objectId!)
query.whereKey("following", equalTo: userids[indexPath.row])
query.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if let objects = objects {
for objects in objects {
objects.deleteInBackground()
}
}
})
}
}
}

Answer 1

(PFUser.currentUser()?.objectId)!
or the query-var is nil. That causes the exception.
You should probably use the if let construct
if let objectId = PFUser.currentUser()?.objectId {
query.whereKey("follower", equalTo: objectId)
}
or if the code should be just executed when all the values exist you can use the guard keyword.
guard let a = optionalType?.variable?.a, b = optionalType?.variable?.b else { return }