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

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

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

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])
}

}