App's Life Cycle 화면생명주기, AppDelegate, SceneDelegate

화면생명주기와, 앱의 생명주기가 있다. 

화면생명주기와 앱의 생명주기를 분리해서 생각하자.

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⭐️ 화면생명주기 뷰컨트롤러에서 실행

viewDidLoad() - 뷰의 로딩이 완료되었을때 시스템에 의해 자동으로 호출됨(메모리에 올림)

리소스를 초기화하거나 초기화면을 구성하는 용도로 사용

처음 한번만 실행해야하는 초기화 코드가 잇을 경우 여기에 작성한다.

viewWillAppear() - 뷰가 나타나기 직전에 호출

다른뷰로 갔다가 다시 돌아오는 상황에 해주고 싶은 처리

ex) 팝업창 띄울때 / 화면을 다가리는 팝업과 풀페이지의 생명주기가 다름

 

viewDidAppear() - 뷰가 화면에 나타나 직후에 실행됨.

뷰가 나타났다는 것을 컨트롤러에게 알림, 화면에 적용될 애니메이션을 그려줌

이것을 제외하고 viewDidAppear와 viewWillAppear는 거의 비슷

 

viewWillDisappear() - 뷰가 사라지기 직전에 호출

뷰가 삭제 되려고 하고 있는 것을 뷰컨트롤러에 통지

 

viewDidDisappear()  - 뷰컨트롤러의 뷰가 제거 되었음을 알려줌

 

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⭐️ 앱의생명주기 SceneDelegate에 있는 내용

import UIKit

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
        guard let _ = (scene as? UIWindowScene) else { return }
    }

    func sceneDidDisconnect(_ scene: UIScene) {
        // Called as the scene is being released by the system.
        // This occurs shortly after the scene enters the background, or when its session is discarded.
        // Release any resources associated with this scene that can be re-created the next time the scene connects.
        // The scene may re-connect later, as its session was not necessarily discarded (see `application:didDiscardSceneSessions` instead).
    }

    func sceneDidBecomeActive(_ scene: UIScene) {
        // Called when the scene has moved from an inactive state to an active state.
        // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
    }

    func sceneWillResignActive(_ scene: UIScene) {
        // Called when the scene will move from an active state to an inactive state.
        // This may occur due to temporary interruptions (ex. an incoming phone call).
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Called as the scene transitions from the background to the foreground.
        // Use this method to undo the changes made on entering the background.
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Called as the scene transitions from the foreground to the background.
        // Use this method to save data, release shared resources, and store enough scene-specific state information
        // to restore the scene back to its current state.
    }


}

https://developer.apple.com/documentation/uikit/app_and_environment/managing_your_app_s_life_cycle/

Apple Developer Documentation

https://medium.com/good-morning-swift/ios-view-controller-life-cycle-2a0f02e74ff5

iOS View Controller Life Cycle

https://subscription.packtpub.com/book/application-development/9781783550814/6/ch06lvl1sec60/uiviewcontroller-lifecycle-methods

UIViewController lifecycle methods | Learning Xamarin Studio

 

참고글

https://sihyungyou.github.io/iOS-lifecycle/

iOS) 앱/Scene 생명주기