Not passing the code challenge: iOS AutoLayout

Question

Can anyone see what's missing? I keep getting a "Bummer! Try again!" message. Thanks in advance.

layout.swift

class MyViewController: UIViewController {

    let sampleView = UIView()

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

    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        sampleView.translatesAutoresizingMaskIntoConstraints = false
        setupSampleViewConstraints()
        // Add constraints below
    }

    func setupSampleViewConstraints() { 

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

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

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

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

    view.addConstraints([CenterX, CenterY, Height, Width])

    }

}

Answer 1 · 2017-09-07T08:32:44Z

September 7, 2017 8:32am

Your problem here is that you're specifying .notAnAttribute in the 2nd attribute parameter in your constraints to center along both the X and y axes. For these, the centering attribute is an attribute, and you'll need to specify the proper attribute twice to keep the center of sampleView equal to the center of its superview. The code would look something like this:

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

Between you and me, though, I like dealing with AutoLayout in code about as much as I like taking a swift kick to the face. I've never used it like this personally. I've always dealt with it via Interface Builder, and once with PureLayout, and both ways are much nicer

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michaellesniak

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Not passing the code challenge: iOS AutoLayout

1 Answer

Michael Hulet

Michael Hulet

michaellesniak

michaellesniak