Don't understand what I am doing wrong here. Error says I am not adding all the constraints from the question?

Question

Can't understand what my error is here. Height, weight, a centerX and a centerY. I must be missing something....

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: view, attribute: .NotAnAttribute, multiplier: 1.0, constant: 50)
        let sampleViewWidthConstraint = NSLayoutConstraint(item: sampleView, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .NotAnAttribute, multiplier: 1.0, constant: 50)
        let sampleViewCenterXConstraint = NSLayoutConstraint(item: sampleView, attribute: .CenterX, relatedBy: .Equal, toItem: view, attribute: .CenterX, multiplier: 1.0, constant: 0)
        let sampleViewCenterYConstraint = NSLayoutConstraint(item: sampleView, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1.0, constant: 0)
  view.addConstraints ([sampleViewHeightConstraint,
                        sampleViewWidthConstraint,
                        sampleViewCenterXConstraint,
                        sampleViewCenterYConstraint])
}

}

Answer 1 · 2016-10-04T07:41:50Z

October 4, 2016 7:41am

Glad that you figured it out already. Since iOS 9 there is a cleaner way to write LayoutConstraints. You could achieve the same result with the following code:

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

This example is written in Swift 2.2. There are some changes in Swift 3, but they are easy to understand.

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Jonathan Law

Jonathan Law

Don't understand what I am doing wrong here. Error says I am not adding all the constraints from the question?

Jonathan Law

Jonathan Law

1 Answer

Moritz Lang

Moritz Lang