Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Introduction to Auto Layout in iOS Auto Layout in Code Constraints in Code

Posted by jc laurent
jc laurent
6,351 Points

Don't forget to add the constraints to the parent view! that's not what i'm doing?

where is the parent view then?

layout.swift 
class MyViewController: UIViewController {

    let sampleView = UIView()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(sampleView)
    }

    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()

       sampleView.translatesAutoresizingMaskIntoConstraints = false

        // Add constraints below

        let sampleViewHeightConstraint = NSLayoutConstraint(item: sampleView, attribute: .Height, relatedBy: .Equal, 
        toItem: nil, attribute: .NotAnAttribute, multiplier: 1.0, constant: 50.0)

        let sampleViewWidthConstraint = NSLayoutConstraint(item: sampleView, attribute: .Width, relatedBy: .Equal, 
        toItem: nil, attribute: .NotAnAttribute, multiplier: 1.0, constant: 50.0)

         let sampleViewCenterXConstraint = NSLayoutConstraint(item: sampleView, attribute: .CenterX, relatedBy: .Equal, 
        toItem: nil, attribute: .CenterX, multiplier: 1.0, constant: 50.0)

        let sampleViewCenterYConstraint = NSLayoutConstraint(item: sampleView, attribute: .CenterY, relatedBy: .Equal, 
        toItem: nil, attribute: .CenterY, multiplier: 1.0, constant: 50.0)



        view.addConstraints([sampleViewHeightConstraint,sampleViewWidthConstraint,sampleViewCenterXConstraint,
        sampleViewCenterYConstraint])
    }
}

2 Answers

Moritz Lang
Moritz Lang
25,909 Points
Moritz Lang
Moritz Lang
25,909 Points

I think here you'd finish the challenge with my answer from your other AutoLayout question :)

Frank Quemuel
Frank Quemuel
5,479 Points
Frank Quemuel
Frank Quemuel
5,479 Points

I messed around with the code and got the correct answer. Go figure. To sum it up, when I changed sampleView.translateAutoresizingMaskIntoConstraints into "true", it worked.

  // Add constraints below
            sampleView.translatesAutoresizingMaskIntoConstraints = true

        let sampleViewCenterX = NSLayoutConstraint(item: sampleView, attribute: .centerX, relatedBy: .equal, toItem: view, attribute: .centerX, multiplier: 1.0, constant: 0.0)

        let sampleViewCenterY = NSLayoutConstraint(item: sampleView, attribute: .centerY, relatedBy: .equal, toItem: view, attribute: .centerY, multiplier: 1.0, constant: 0.0)

        let sampleViewHeight = NSLayoutConstraint(item: sampleView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 50.0)

        let sampleViewWidth = NSLayoutConstraint(item: sampleView, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 50.0)

        view.addConstraints([
            sampleViewWidth,
            sampleViewHeight,
            sampleViewCenterX,
            sampleViewCenterY])
}

}