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ViewDidAppear and viewDidDisappear callback sequence between two view controllers

As I know, there are at least two ways to present a UIViewController on another UIViewController, first uses presentModalViewController: animated: on UIViewController, the other uses pushViewController: animated: on UINavigationController, it seems when 2 view controllers change their appearance, causing the callback to appear / disappear different. The following is an example: A is the UINavigationController, and B is the normal view controller, the actual callback sequence:
(1) A using presentModalViewController: animated: to display B:

[B viewWillAppear]; [A viewWillDisappear]; [B viewDidAppear]; [A viewDidDisappear];

(2) A using pushViewController: animated: to display B:

 [A viewWillDisappear]; [B viewWillAppear]; [A viewDidDisappear]; [B viewDidAppear];

So my question is: are these different callback sequences stable, or is there no specific sequence that we can rely on? If they are stable, is there a document in the document? Can anyone help? Thanks, advanced!

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2 answers

UIKit should work on the main thread, so I assume the sequence is stable for the current version of the SDK . However, as long as the behavior is not documented (and as far as I know), I would consider it subject to change without notice.

I'm just curious; why do you need a deterministic sequence of these methods? Perhaps you can find a workaround (which could do this better).

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You will definitely want to implement some form of synchronization to ensure what you want to do. Building on Apple, the defiant sequence of these features simply asks about problems.

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Source: https://habr.com/ru/post/918788/

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