Autolayout take no effect

Question

I just start to study swift, and when I use Cartography to autolayout views, I have a problem. Here is what happens.

I create a LoginViewController, put all the constrains in a function named "updateConstrains()", and called in the override func viewDidLoad(). If I set the LoginViewController as the window rootViewController in AppDelegate, it works well.

But if I put the LoginViewController as the rootViewController of a UINavigationController as follows:

window!.rootViewController = UINavigationController(rootViewController: loginViewController)

It become like this:

and when print the width and height of the LoginViewController's view. It turns out that:

width = 155, height = 0.

Can anyone tell me what happens?

Answer 1

A common cause for this is forgetting to set translatesAutoresizingMaskIntoConstraints = false on the view.

Views which are instanced in code have this property set to true by default. This creates a set of auto layout constraints based on the values of autoresizingMask. If the autoresizing mask is not correctly defined, which is often the case when auto-layout is used, then the generated constraints will not be what you intended.

See the Apple documentation for translatesAutoresizingMaskIntoConstraints and autoresizingMask