Segue value nil in ViewDidLoad but has value in didSet

Question

I am passing a Core Data entity to the next View Controller with a prepareForSegue like this:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "MemberDetails" {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewControllerWithIdentifier("MemberDetails") as! MemberDetails
        let index = self.memberTable.indexPathForSelectedRow
        if searchPredicate == nil {
            let member = self.sections[index!.section].members[index!.row]
            member.printMember()
            vc.member = member
        } else {
            vc.member = self.filteredMembers[index!.row]
        }

    }
}

And in my receiving View Controller i have this:

var member : Member? {
    didSet {
        print("")
        print(" --------------------- ")
        print("")
        member?.printMember()
    }
}

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.

    print("")
    print(" --------View Did Load -------- ")
    print("")
    self.member?.printMember()
}

With the following output:

----------_-----------

// member.printMember() function output

--------View Did Load --------

// no ouput -> object is nil

This means that the didSet happens before the viewDidLoad and it has values but for some reason it is emptied again when the viewDidLoad is executed (object = nil)

Why is this happening? / How do i mitigate this effect?

score 2 · Accepted Answer · answered Jun 29 '16 at 18:34

I think you misunderstood what a segue is.

You are instantiating a new MemberDetails on prepareForSegue

 let storyboard = UIStoryboard(name: "Main", bundle: nil)
 let vc = storyboard.instantiateViewControllerWithIdentifier("MemberDetails") as! MemberDetails

If the prepareForSegue method is called, this means a viewController from the storyboard is already being loaded

what you need is

if segue.identifier == "MemberDetails" {
      if let vc = segue.destinationViewController as? MemberDetails{
           let index = self.memberTable.indexPathForSelectedRow
           if searchPredicate == nil {
                let member = self.sections[index!.section].members[index!.row]
                member.printMember()
                vc.member = member
           } else {
                vc.member = self.filteredMembers[index!.row]
           }
       }
}

Oh oops indeed. After the first line from your answer i saw the mistake! Thank you very much! — Emptyless, Jun 29 '16 at 18:37

Segue value nil in ViewDidLoad but has value in didSet

1 Answers1