Open Radar

 
Area:
UIKit

Summary:
The following application architecture:

- UITabBarController (root)
-- UINavigationController (delegate = AppDelegate or any other object)
-- UINavigationController (delegate = AppDelegate or any other object)
-- ...

causes duplicate delegate calls to the following UINavigationControllerDelegate method if the navigation controller in the tab bar controller hasn't been loaded yet and is being selected in the tab bar:

func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool)

every consequential selection of the view controller in the tab bar causes correctly just one call.

Steps to Reproduce:
1. Launch provided sample code (Sample.xcodeproj)
2. Toggle console ON
3. Switch to "Second" tab (not loaded yet)
>> logs 2 lines
4. Switch to "Third" tab (not loaded yet)
>> logs 2 lines
5. Switch back to any tab (all are loaded now)
>> logs 1 line

Expected Results:
Each tab selection should only call the UINavigationControllerDelegate method once

Actual Results:
For controllers that are still not loaded the UINavigationControllerDelegate method is being called twice

Version:
iOS 10

Notes:


Configuration:
iPhone 7

Attachments:
'Sample.zip' was successfully uploaded.