I am working on a camera app where the camera views are shown modally. After I am done with cropping. I perform an unwind segue to the MainPageViewController. (         
        
I want to provide my own solution to this problem for now. Any further answers are always welcome.
I put a boolean variable and viewDidAppear function to MainPageViewController.
var fromCamera = false
override func viewDidAppear(animated: Bool) {
    if fromCamera {
        self.performSegueWithIdentifier("categorySelection", sender: self)
        self.fromCamera = false
    }
}
I set fromCamera to true before I perform unwind segue from CropViewController. By that way, I perform segue to category screen only if an unwind segue from crop view is performed.