viewDidLoad not called when initialising obj viewcontroller from Swift

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

I don't see you presenting the view controller. Does it even show up? — saagarjha, Aug 16 '15 at 17:48
`viewDidLoad` shouldn't be called for either of those two lines. `viewDidLoad` is called the first time the `view` property of the view controller is accessed. That doesn't normally happen just by instantiating the view controller. Typically it happens when first trying to display the view controller. — rmaddy, Aug 16 '15 at 17:48
I you are using [[DetailMessageViewController alloc] init]; then viewDidLoad will not call automatically, you need to call [self.detilVc loadView] — Adnan Aftab, Aug 16 '15 at 17:57
you probably don't want to call loadView by itself, this can cause a recursive cycle memory leak where viewDidLoad isn't called, you may just want to do something like this if you really need to, but I can't see a case when this is really needed: YOURViewController * so = [[YOURViewController alloc] init]; UIView * what=so.view; this will cause the view to be preloaded and will call ViewDidLoad as wll to prevent side effects, but again, I don't see a reason why you would want to do this very often — Larry Pickles, Aug 16 '15 at 18:06
@C_X Never call `loadView` directly. The docs even tell you that. — rmaddy, Aug 16 '15 at 18:08
the only way you should be calling loadView is like this, and this means you are using programmatic views: -(void)loadView { [self setView:[NSHSplashScreenView new]]; } -(NSHSplashScreenView*)contentView { return (id)[self view]; } — Larry Pickles, Aug 16 '15 at 18:09
yes and docs also say use initWithNibName:bundle: (if you don't have nib pass nil reset it will handle) — Adnan Aftab, Aug 16 '15 at 18:09
Ill have to try that one, C_X, from my experience if you call loadView like you show then then view of the view controller doesn't have a point of reference to set it's views and thereby doesn't have a "window" size to work with yet so it crashes, and crashes very badly with a recursive call to itself — Larry Pickles, Aug 16 '15 at 18:12

score 1 · Accepted Answer · edited May 23 '17 at 11:44

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.

The behavior is normal but sometimes you need to tell UIKit to load the view if this hasn't been done. Mostly when using Xib. This is done by calling vc.loadViewIfNeeded() — iDev, Jul 13 '17 at 14:15

score 0 · Answer 2 · answered Jul 13 '17 at 14:10

0

For iOS 9+ you can call vc.loadViewIfNeeded().

answered Jul 13 '17 at 14:10

iDev

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viewDidLoad not called when initialising obj viewcontroller from Swift

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