How to do some stuff in viewDidAppear only once?

by

There is a standard, built-in method you can use for this.

Objective-C:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    if ([self isBeingPresented] || [self isMovingToParentViewController]) {
        // Perform an action that will only be done once
    }
}

Swift 3:

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    if self.isBeingPresented || self.isMovingToParentViewController {
        // Perform an action that will only be done once
    }
}

The call to isBeingPresented is true when a view controller is first being shown as a result of being shown modally. isMovingToParentViewController is true when a view controller is first being pushed onto the navigation stack. One of the two will be true the first time the view controller appears.

No need to deal with BOOL ivars or any other trick to track the first call.

More Related Contents:

  1. Swift – how to read data from many UITextFields which generate data by UIPickerView [closed]
  2. iPhone get SSID without private library
  3. Placeholder in UITextView
  4. @property retain, assign, copy, nonatomic in Objective-C
  5. Looping a video with AVFoundation AVPlayer?
  6. Dismiss keyboard by touching background of UITableView
  7. iOS: Modal ViewController with transparent background
  8. Changing root view controller of a iOS Window
  9. Why are didBeginContact called multiple times?
  10. getting data out of a closure that retrieves data from firebase
  11. Cannot put a google maps GMSMapView in a subview of main main view?
  12. How to put a logo in NavigationView in SwiftUI?
  13. Xcode 6 isn’t autocompleting in Swift
  14. Simple way to change the position of UIView?
  15. distanceFromLocation – Calculate distance between two points
  16. Could not load the “” image referenced from a nib in the bundle with identifier
  17. Redirect NSLog to File in Swift not working
  18. Real time blur effect for Navigation Bar
  19. How can I delay a method call for 1 second?
  20. iOS: How do you find the creation date of a file?
  21. How can I implement a swiping/sliding animation between views?
  22. UIWebView and Safari comparison
  23. SwiftUI 2.0 List with children – how to make the tappable area of the disclosure button cover the whole list item
  24. EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) on dispatch_semaphore_dispose
  25. AVSpeechSynthesizer in background mode
  26. Swift – How to record video in MP4 format with UIImagePickerController?
  27. How To Disable AFNetworking Cache
  28. What’s the state of developing iOS apps in Linux? [closed]
  29. Parse + Stripe iOS main.js
  30. UICollectionView current visible cell index

Leave a Comment