iOS-具有对父视图控制器的“强大”引用的子视图控制器

来自UIViewController.h。

/*
  If this view controller is a child of a containing view controller (e.g. a navigation controller or tab bar
  controller,) this is the containing view controller.  Note that as of 5.0 this no longer will return the
  presenting view controller.
*/
weak public var parentViewController: UIViewController? { get }

和

// An array of children view controllers. This array does not include any presented view controllers.
@available(iOS 5.0, *)
public var childViewControllers: [UIViewController] { get }

在这里，您可以看到parent和child之间已经存在 strong和weak引用ViewControllers。您不应strong在从子级到父级的方向上添加更多新引用，因为这可能导致内存泄漏。