原文地址::https://blog.csdn.net/chokshen/article/details/82314944
项目中经常出现一个控制器添加多个子控制器的情况，例如今日头条的标签切换视图，使用addChildViewController的正确姿势如下：
先添加第一个控制器，其余控制器暂时不用添加：
//A控制器
let vcA = ViewControllerA()
self.addChildViewController(vcA)
vcA.didMove(toParentViewController: self)
currentVC = vcA
vcA.view.frame = self.view.bounds
self.view.addSubview(vcA.view)
点击按钮，切换子控制器：
@objc func change(_ sender: UISegmentedControl) {
if sender.selectedSegmentIndex == 0 {
changeController(from: currentVC, to: ViewControllerA())
} else if sender.selectedSegmentIndex == 1 {
changeController(from: currentVC, to: ViewControllerB())
} else if sender.selectedSegmentIndex == 2 {
changeController(from: currentVC, to: ViewControllerC())
}
}
func changeController(from oldController: UIViewController, to newController: UIViewController) {
if currentVC != newController {
self.addChildViewController(newController)
newController.view.frame = self.view.bounds
self.transition(from: oldController, to: newController, duration: 0.3, options: .curveEaseInOut, animations: {
}) { (finished) in
if finished {
newController.didMove(toParentViewController: self)
oldController.willMove(toParentViewController: nil)
oldController.removeFromParentViewController()
self.currentVC = newController
}
}
}
}
经过测试，使用这种方式切换子控制器，旧的控制器会被释放，新的控制器会重新加载。