在将其添加为子视图后，Deinit UIViewController

Question

我需要添加一个视图控制器作为mt 当前视图的子视图，但在不再需要它后无法初始化

let viewController = CountrySelectViewController()
viewController.view.frame = self.view.bounds
viewController.view.alpha=0
self.view.addSubview(viewController.view)
UIView.animate(withDuration: 0.25, delay: 0.0, options: [], animations: {
viewController.view.alpha=1
}, completion: { (finished: Bool) in
})
viewController.completionHandlerClose = {
UIView.animate(withDuration: 0.25, delay: 0.0, options: [], animations: {
viewController.view.alpha=0
}, completion: { (finished: Bool) in
viewController.view.removeFromSuperview()
viewController.view = nil
})
}

Answer 1

有一个明显的强引用循环，必须使用weak引用来打破：

viewController.completionHandlerClose = { [weak viewController] in
guard let controller = viewController else { return }
UIView.animate(
withDuration: 0.25,
delay: 0.0,
options: [],
animations: {
controller.view.alpha = 0
},
completion: { _ in
controller.view.removeFromSuperview()
controller.view = nil
}
)
}

见 https://docs.swift.org/swift-book/LanguageGuide/AutomaticReferenceCounting.html