从 Swift 初始化 obj viewcontroller 时未调用 viewDidLoad

Question

In my Swift code, I am trying to instantiate an Objective-C view controller like below, however the viewDidLoad method is not being called.

let detailMessageVC = DetailMessageViewController(nibName:nil, bundle:nil)

If I instantiate the same viewcontroller from Objective-C code like this it does get called. There is no xib for the view controller.

self.detailMVC = [[DetailMessageViewController alloc] init];

Does anyone know why this is happening? I would like to have the same behaviour when calling from Swift as I rely on the viewDidLoad to perform various initialisation. This is with Xcode 6.3.2

Answer 1

As comment stated, there is no link between initialisation of a view controller and it's viewDidLoad callback.

You can even have viewDidLoad called before init. Because viewDidLoad is called if the ViewController effectively loaded a view.

Check there : https://stackoverflow.com/a/4862772/1486230

Although, I wouldn't rely on viewDidLoad unless you know that you will effectively display your ViewController; Mostly by using myVC.view .

Just think like initialising a ViewController (which is only a logic object) is different than creating its view. For performance reason, iOS won't create the graphic object if they are not needed. If you get a difference between Swift and Objective-C, it's more because Swift is probably better on optimisation. But the behaviour is normal.

Answer 2

对于 iOS 9+，您可以调用vc.loadViewIfNeeded() 。