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

Sheng Wei
Sheng Wei
4,382 Points
Posted by Sheng Wei
Sheng Wei
4,382 Points

[Help!] What is wrong with my constraint?

The bummer keeps saying that I haven't linked it to the parent view...can someone tell me what the syntax for it is? Thanks!

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
           func setUpsampleViewConstraints() { 
            sampleView.translatesAutoresizingMaskIntoConstraints = false    
            }

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

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

            let sampleViewCenterXConstraint = NSLayoutConstraint(item: sampleView, attribute: .CenterX, relatedBy: .Equal, 
            toItem: nil, attribute: .CenterX, multiplier: 1.0, constant: 0.0)

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

    }
}

1 Answer

Jairo Eli de Leon
Jairo Eli de Leon
5,182 Points
Jairo Eli de Leon
Jairo Eli de Leon
5,182 Points

Same here, I am not sure what the problem is. So I took few video lessons and then back to this challenge again but this time I created constraints using layout anchors. It worked for me!

NSLayoutConstraint.activateConstraints([
  sampleView.heightAnchor.constraintEqualToConstant(50.0),
  sampleView.widthAnchor.constraintEqualToConstant(50.0),
  sampleView.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor),
  sampleView.centerYAnchor.constraintEqualToAnchor(view.centerYAnchor)
  ])