Swift NSLayoutConstraint sample

//: Playground - noun: a place where people can play

import UIKit


class CustomView: UIView {

    var titleLabel: UILabel!
    var messageLabel: UILabel!

    override init(frame: CGRect) {
        super.init(frame: frame)

        layoutLabels()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func awakeFromNib() {
        super.awakeFromNib()

        layoutLabels()

    }

    func layoutLabels() {

        let tFrame = CGRect(x: 10, y: 10, width: frame.width - 20, height: 40)
        titleLabel = UILabel(frame: tFrame)
        addSubview(titleLabel)


        let mFrame = CGRect(x: 10, y: 60, width: frame.width - 20, height: 40)
        messageLabel = UILabel(frame: mFrame)
        addSubview(messageLabel)

        // add constraints programmatically

        let tLead = NSLayoutConstraint(item: titleLabel, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1, constant: 10)
        let tTop = NSLayoutConstraint(item: titleLabel, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1, constant: 10)
        let tTrail = NSLayoutConstraint(item: titleLabel, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1, constant: 10)
        addConstraints([tLead, tTop, tTrail])

        let tHeight = NSLayoutConstraint(item: titleLabel, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 40)
        titleLabel.addConstraint(tHeight)

        let mLead = NSLayoutConstraint(item: messageLabel, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1, constant: 10)
        let mTop = NSLayoutConstraint(item: messageLabel, attribute: .top, relatedBy: .equal, toItem: titleLabel, attribute: .bottom, multiplier: 1, constant: 10)
        let mTrail = NSLayoutConstraint(item: messageLabel, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1, constant: 10)
        addConstraints([mLead, mTop, mTrail])

        let mHeight = NSLayoutConstraint(item: messageLabel, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 40)
        messageLabel.addConstraint(mHeight)

        titleLabel.backgroundColor = .green
        messageLabel.backgroundColor = .red

    }
}

let this = CustomView(frame: CGRect(x: 0, y: 0, width: 500, height: 200))

print(this.subviews)