How to get the previous viewcontroller that pushed my current view

Question

The home page of my app has UIButtons, btnIncome and btnExpense. Pressing on this buttons pushes IncomeVC and Expen

Answer 1

Swift

extension UINavigationController {
    func getPreviousViewController() -> UIViewController? {
        let count = viewControllers.count
        guard count > 1 else { return nil }
        return viewControllers[count - 2]
    }
}

Answer 2

In Swift:

let n: Int! = self.navigationController?.viewControllers?.count
let myUIViewController = self.navigationController?.viewControllers[n-2] as! UIViewController

Answer 3

Swift 3

Here is a mashup of the previous answers that can be put into an extension:

extension UIViewController{
   var previousViewController:UIViewController?{
        if let controllersOnNavStack = self.navigationController?.viewControllers, controllersOnNavStack.count >= 2 {
            let n = controllersOnNavStack.count
            return controllersOnNavStack[n - 2]
        }
        return nil
    }
}

Edit:

When fetching the previousViewController of a given view controller, call it VC1, in viewWillDisappear, VC1 is already popped of the Navigation Controller Stack. So in this scenario, the above code does not end up fetching the View controller directly above VC1(call it VC2), but the view controller above VC2 (if it exists).

To avoid this problem I just check if VC1 is still on the stack when previousViewController is requested. Here is the updated code:

extension UIViewController{
    var previousViewController:UIViewController?{
        if let controllersOnNavStack = self.navigationController?.viewControllers{
            let n = controllersOnNavStack.count
            //if self is still on Navigation stack
            if controllersOnNavStack.last === self, n > 1{
                return controllersOnNavStack[n - 2]
            }else if n > 0{
                return controllersOnNavStack[n - 1]
            }
        }
        return nil
    }
}

This code assumes that view controller you are sending the previousViewController message to will either be at the top of the navigation stack or not at all.

Answer 4

In Swift 3,

if let navController = self.navigationController, navController.viewControllers.count >= 2 {
     let viewController = navController.viewControllers[navController.viewControllers.count - 2]
}