Subscribe to UINavigationController back button with RxSwift / RxCocoa

问题

I have a simple test project with a UINavigationController as my rootViewController.

I push the first ViewController which has a + button as right bar button item, I subscribe to its taps to present a new ViewController (which is identical to the previous one). The push segue works as I expect.

UIKit manages the back button for me and I think it is UINavigationController that makes the magic behind the scene.

Now, what I need to do is subscribe to the back button, but I can't find how to do this. I have tried with

1. navigationController.navigationBar.backItem?.backBarButtonItem?.rx.tap

2. navigationController.navigationItem.backBarButtonItem?.rx.tap but they seem to be nil, so the optional chaining prevents subscription.

Thanks for your help, Luca-

回答1:

I think your best bet here is to use the operator on UINavigationController.

navigationController.rx.willShow will trigger whenever a view controller is about to be shown. You can do any last minute clean up when it fires.

来源：https://stackoverflow.com/questions/44609844/subscribe-to-uinavigationcontroller-back-button-with-rxswift-rxcocoa