Programmatically creating constraints bound to view controller margins

I'm trying to make a view that will act as a sort of "panel", attached to the right side of the view controller.

That is, it is bound to the trailing, top, and bottom margins of the parent view controller, with a static width of 300

However, I just can't seem to get it right, I'm either breaking a constraint or doing something xcode tells me is illegal.

What am I doing wrong?

Here is the code in the controller

    let myView = UIView()
    view.backgroundColor = UIColor.redColor()
    self.view.addSubview(view)
    let topConstraint = NSLayoutConstraint(item: myView,
                                           attribute: .Top,
                                           relatedBy: .Equal,
                                           toItem: self.topLayoutGuide,
                                           attribute: .Bottom,
                                           multiplier: 1,
                                           constant: 0)

    let trailingConstraint = NSLayoutConstraint(item: self.view,
                                                attribute: .TrailingMargin,
                                                relatedBy: .Equal,
                                                toItem: myView,
                                                attribute: .Trailing,
                                                multiplier: 1,
                                                constant: 0)

    let bottomConstraint = NSLayoutConstraint(item: self.bottomLayoutGuide,
                                              attribute: .Top,
                                              relatedBy: .Equal,
                                              toItem: myView,
                                              attribute: .Bottom,
                                              multiplier: 1,
                                              constant: 0)

    let widthConstraint = NSLayoutConstraint(item: myView,
                                             attribute: .Width,
                                             relatedBy: .Equal,
                                             toItem: nil,
                                             attribute: .NotAnAttribute,
                                             multiplier: 1,
                                             constant: 300)

    self.view.addConstraints([trailingConstraint])
    view.addConstraints([topConstraint, bottomConstraint, widthConstraint])

Solution

Actually the problem in your code is that you did not set the translatesAutoresizingMaskIntoConstraints of myview to false, whenever you want to use auto-layout constraints then you have to set translatesAutoresizingMaskIntoConstraints of a view to false. Another Problem is that you do not add myview on self.view I have updated your code and Its working fine According your constraints.

Put below code in your ViewController .

let myView = UIView()
myView.backgroundColor = UIColor.redColor()
self.view.addSubview(myView)
myView.translatesAutoresizingMaskIntoConstraints = false

view.addConstraint(NSLayoutConstraint(item: myView, attribute: .Top, relatedBy: .Equal, toItem: self.topLayoutGuide, attribute: .Bottom, multiplier: 1, constant: 0))
view.addConstraint(NSLayoutConstraint(item: myView, attribute: .Bottom, relatedBy: .Equal, toItem: self.bottomLayoutGuide, attribute:.Top, multiplier: 1, constant: 20))

view.addConstraint(NSLayoutConstraint(item: myView, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute,multiplier: 1, constant: 300))
view.addConstraint(NSLayoutConstraint(item: myView, attribute: .TrailingMargin, relatedBy: .Equal, toItem: view, attribute: .TrailingMargin, multiplier: 1, constant: 0))