Breaking News: Grepper is joining You.com. Read the official announcement!

view controller life cycle

Murad_9288 answered on October 18, 2022 Popularity 9/10 Helpfulness 4/10

answer view controller life cycle

view controller life cycle

Comment

View Controller lifecycle

This is the second responsibility of a view controller. Whenever a view controller is presented, it goes through the viewWillAppear method and then the viewDidAppear method is invoked.

The same happens when the view disappears: First, the viewWillDisappear method is invoked and then the viewDidDisappear method is invoked.

We can easily check this by modifying the code in our ViewController class.

Differences between methods
As the names suggest, there are small differences between these methods:

viewWillAppear is invoked when the VC is presenting the view, but the view is not yet visible.
viewDidAppear is invoked when the view is already rendered on the screen.
viewWillDisappear is invoked when the VC is about to dismiss the view, but the view is still rendered on the screen
viewDidDisappear is invoked when the view is not rendered anymore.

The interesting bit is line 11, where we present a new ViewController named Modal whenever the user taps on the Present button.

Finally, let’s add some other logs lines for the view lifecycle:

class ViewController: UIViewController {

  // ... init and loading ...
  
  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    self.logMethod()
  }

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

  override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    self.logMethod()
  }

  override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    self.logMethod()
  }
}

// Bangla Explain:

viewDidload() ---> এই মেথডটি একবার ভিউ কন্ট্রোলার লাইফ সাইকেলে লোড করা হয়| এবং মেথডটিতে যখন সমস্ত ভিউ লোড হয় তখন এটি কল হয়।  
viewwillAppear() ---> view visible হবার আগে কল হয়। 
viewWillLayoutSubviews() ---> UI design পরিবর্তন করলেই এটি কল হবে প্রত্যেকবার।  
viewDidLayoutSubViews() ---> সাবভিউ সেট করার পর পরিবর্তন করতে চাইলে এখানে কোড পরিবর্তন করতে হয়। 
viewDidAppear() ---> view sereen-এ  প্রদর্শণ হওয়ার পর এই method কল হয়। 
viewWillDisappear() ---> VC এর ভিউ হায়ারার্কি(hierarchy) থেকে remove হওয়ার আগে এই মেথড কল হয়। 
viewDidDisappear() --->  VC এর ভিউ হায়ারার্কি(hierarchy) থেকে remove হওয়ার পরে এই মেথড কল হয়।

Popularity 9/10 Helpfulness 4/10 Language swift

Source: github.com

Tags: controller cycle lifecycle swift view

Link to this answer
Share Copy Link

Contributed on Oct 18 2022

Murad_9288

0 Answers Avg Quality 2/10

view controller life cycle

Contents

More Related Answers

view controller life cycle

Grepper

Documentation

Social

Legal

Contact

Oops, You will need to install Grepper and log-in to perform this action.