ViewController.swift

//
//  ViewController.swift
//  Tester
//

import UIKit
import Cartography

class ViewController: UIViewController {
    lazy var crashingView: UIView  = {
        UIView(frame: CGRect())

    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        crashingView.backgroundColor = UIColor.purpleColor()
        view.addSubview(crashingView)
       
        // Crashes:
        layout(crashingView) { (crashingView) in
            crashingView.width == crashingView.superview!.width ~ 750
            return
        }
        // Crashes as well:
//        let constraint = NSLayoutConstraint(item: crashingView, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 1, constant: 0)
//        NSLayoutConstraint.activateConstraints([constraint])
//        constraint.priority = 750
    
        // Doesn't Crash
//        let constraint = NSLayoutConstraint(item: crashingView, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 1, constant: 0)
//        constraint.priority = 750
//        NSLayoutConstraint.activateConstraints([constraint])
        
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}