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 perpetual makayi
perpetual makayi
8,441 Points

introduction to Auto layout

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: view, attribute: .CenterX, multiplier: 1.0, constant: 0.0)
    let sampleViewCenterYConstraint = NSLayoutConstraint(item: sampleView, attribute: .CenterY, relatedBy: .Equal,
                                      toItem: view, attribute: .CenterY, multiplier: 1.0, constant: 0.0)

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

}

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: view, attribute: .CenterX, multiplier: 1.0, constant: 0.0)
        let sampleViewCenterYConstraint = NSLayoutConstraint(item: sampleView, attribute: .CenterY, relatedBy: .Equal,
                                          toItem: view, attribute: .CenterY, multiplier: 1.0, constant: 0.0)

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

}