using variables outside of completion block

Question

Im currently retrieving data from firebase the data is put inside an NSObject and then a completion block. The item inside of the completion block is store as a variable userBinfos. Variable userBinfos only work inside of the completion block i want to use this outside of the completion

var userBinfos = userObject()
    override func viewDidLoad() {
        super.viewDidLoad()

        userBinfo { (user) in
        self.userBinfos = user

        }  
//I want to use to variable here but it does not work 
        print(self.userBinfos.email)

    }


    func userBinfo(completion: (userObject) -> ()) {

        let dbFir = FIRDatabase.database().reference()

        let firRef = dbFir.child("frontEnd/users/\(userId)")

        firRef.observeEventType(.Value, withBlock: { snapshot in

            let userDict = snapshot.value as! [String: AnyObject]
            self.name.text = userDict["firstname"] as? String
            self.userBio.text = userDict["userBio"] as! String

            var user = userObject()

            user.firstName = userDict["firstname"]
            user.lastName = userDict["lastname"]
            user.email = userDict["email"]
            user.profileImageUrl = userDict["profileImageUrl"]
            user.userBio = userDict["firstname"]
            user.userId = userDict["firstname"]

                   dispatch_async(dispatch_get_main_queue(), {
            completion(user)

            })

        }) { (error) in
            print(error)
        }

    }

you're calling print(self.userBinfos.email) outside the block!! put it inside: userBinfo { (user) in } so it is being called before it is being assigned by the block — Jad
– Jad, Commented Aug 21, 2016 at 18:02
observeEventType works asynchronously that means the completion block is called later after viewDidLoad finishes. Put the code you want to execute outside the completion block in the block and you are done. — vadian
– vadian, Commented Aug 21, 2016 at 18:03

Rob · Accepted Answer · 2016-08-21 18:56:23Z

The entire purpose of the completion parameter of userBinfo is to provide a mechanism for being informed when the asynchronous observeEventType is called. So put code contingent upon the completion of that asynchronous method inside the userBinfo { user in ... } closure.

And if part of the UI doesn't make sense until that asynchronous completion closure is called, then have viewDidLoad configure the UI to make that explicit (perhaps show a UIActivityIndicatorView or whatever) and then remove that stuff inside the completion handler.

override func viewDidLoad() {
    super.viewDidLoad()

    // do whatever you want to let the user know that something asynchronous
    // is happening, e.g. add a spinning `UIActivityIndicatorView` or whatever

    userBinfo { user in
        self.userBinfos = user

        // Update the UI here, including removing anything we presented to let
        // the user know that the asynchronous process was underway. If you were
        // dealing with UITableView`, you'd call `tableView.reloadData()` here.
    }  

    // but not here
}

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