How to access data outside the Alamofire block using swift 3.0

Question

I've just started 'Alamofire' for JSON parsing. Now I'm facing some problem which are as follow:

Problem Statement : Unable to access data outside the Alamofire block.

Coding Stuff :

import UIKit

import Alamofire

    class ViewController: UIViewController
    {
        var dataValue = String()
        override func viewDidLoad()
        {
            super.viewDidLoad()
            Alamofire.request("url") .responseJSON 
            { response in

                dataValue = response.result.value
                print(dataValue) // It prints value
            }
            print(dataValue) //It does not print any thing or nil.
        }

    }

Answer 1

 var dataValue = String()
 override func viewDidLoad()
 {
   super.viewDidLoad()
   Alamofire.request("url") .responseJSON 
  { response in

     dataValue = response.result.value
     self.myFunction(str: dataValue)
  }
  }

 func myFunction(str: String)
 {
    print("str value ====%@",str)
 }