Force viewDidLoad to fire on iOS

Question

I have two window app and while I present first window I would like the view in second window to load and prepare content for later in background.

I've tried to use method loadView but Apple says you should not call this method directly.

So far I've chosen to use the view's method userInteractionEnabled which actually implicitly calls viewDidLoad method.

Is there an elegant way to force ViewControllers viewDidLoad method to fire before it should naturally (when window is key and presented)?

Demurral

Answer 1

You can just call [viewController view];.

The documentation for UIViewController explains how the view property is lazy-loaded and that viewDidLoad is called after the view is loaded.

Redcoat

So simple yet so powerful :) Thanks! – Demurral

Nice! At first I tried viewController.view but it gave a warning but sending it the message "view" this way doesn't give a warning at all – Alrich

This was exactly what I was looking for, but is there a documentation/explanation on how this works and what it does? – Novation

@Novation Yes the documentation for UIViewController explains how the view property is lazy-loaded and that viewDidLoad is called after the view is loaded. – Redcoat

Answer 2

In iOS 9, Apple finally fixed this:

// Loads the view controller's view if it has not already been set.
@available(iOS 9.0, *)
public func loadViewIfNeeded()

Masqat

Here is the real answer – Hyetal

Answer 3

Swift 2.0, with same result of @Carl Veazey's solution:

let viewController = MyCustomViewController()
_ = viewController.view

Attorneyatlaw

I am trying this with swift and it's not working... Did this stop working with the newer versions of iOS/Swift? – Furlana

What do you mean with "newer versions of iOS/Swift"? Swift 3.0? I didn't test Swift 3.0 yet, so I don't know If this approach still works. – Ables

I am using swift 2.2, and this is not working for me... The only difference between my code and yours is that instead of instatiating the View Controller myself, I am calling the method instantiateViewControllerWithIdentifier of the storyboard instance. – Furlana

My bad, I was instantiating a NavigationController, that's why it wasn't working... Thank you – Furlana

Ok, no problem. I've just test and confirm that It still works! ;) – Ables

Answer 4

You can create a global instance for that controller(May be in AppDelegate) and call the method you want to perform the action for. Then While pushing to that controller don't create a new instance Just use the instance you have created for global use.

Sverre