How do I set adaptive multiline UILabel text?

I kind of got things working by adding auto layout constraints:

But I am not happy with this. Took a lot of trial and error and couldn't understand why this worked.

Also I had to add to use titleLabel.numberOfLines = 0 in my ViewController

I know it's a bit old but since I recently looked into it :

let l = UILabel()
l.numberOfLines = 0
l.lineBreakMode = .ByWordWrapping
l.text = "BLAH BLAH BLAH BLAH BLAH"
l.frame.size.width = 300
l.sizeToFit()

First set the numberOfLines property to 0 so that the device understands you don't care how many lines it needs. Then specify your favorite BreakMode Then the width needs to be set before sizeToFit() method. Then the label knows it must fit in the specified width