Weird issue when setting up auto-layout constraints in code

I want to have a footer view on a static-cell UITableView that has three labels which are equally spaced, like so (from the simulator):

I can supply the footer view from my table view controller using this delegate call:

override func tableView(tableView: UITableView, viewForFooterInSection section: Int) -> UIView? {
    // construct view here
    return view
}

And I can construct the view in two ways:

• Create the labels and the spacers in code and add the appropriate constraints
• Do all that in a XIB file then load the view from the file

My problem is that the first approach doesn't work and the second does.

This is my code for the first approach:

override func tableView(tableView: UITableView, viewForFooterInSection section: Int) -> UIView? {

    if section == 0 {

        // Create footer view
        let view = UIView()
        view.backgroundColor = UIColor.yellowColor()
        view.clipsToBounds = false
        view.layer.borderColor = UIColor.greenColor().CGColor
        view.layer.borderWidth = 2
        view.setTranslatesAutoresizingMaskIntoConstraints(false)

        // Create labels
        var labels: [UIView] = []
        for name in ["Label 1", "AAAAAABBB", "Last label"] {
            let v = UILabel()

            v.font = UIFont.preferredFontForTextStyle(UIFontTextStyleFootnote)
            v.textColor = UIColor.darkTextColor()
            v.textAlignment = .Center
            v.text = name
            v.setTranslatesAutoresizingMaskIntoConstraints(false)

            view.addSubview(v)
            labels += [v]
        }

        // Create spacers
        var spacers: [UIView] = []
        for i in 1...4 {
            let v = UIView()

            v.backgroundColor = UIColor.blueColor() // Background color is just so we can see where the view is and what size it has
            v.setTranslatesAutoresizingMaskIntoConstraints(false)

            view.addSubview(v)
            spacers += [v]
        }

        // Constrain all views to top and bottom of superview
        for i in labels + spacers {
            view.addConstraint(NSLayoutConstraint(item: i, attribute: .Top, relatedBy: .Equal, toItem: view, attribute: .Top, multiplier: 1, constant: 0))
            view.addConstraint(NSLayoutConstraint(item: i, attribute: .Bottom, relatedBy: .Equal, toItem: view, attribute: .Bottom, multiplier: 1, constant: 0))
        }

        // Equal width for labels
        labels.pairs {
            view.addConstraint(NSLayoutConstraint(item: $0, attribute: .Width, relatedBy: .Equal, toItem: $1, attribute: .Width, multiplier: 1, constant: 0))
        }

        // Equal width for spacers
        spacers.pairs {
            view.addConstraint(NSLayoutConstraint(item: $0, attribute: .Width, relatedBy: .Equal, toItem: $1, attribute: .Width, multiplier: 1, constant: 0))
        }

        view.addConstraint(NSLayoutConstraint(item: view, attribute: .Left, relatedBy: .Equal, toItem: spacers[0], attribute: .Left, multiplier: 1, constant: 0))
        view.addConstraint(NSLayoutConstraint(item: spacers[0], attribute: .Right, relatedBy: .Equal, toItem: labels[0], attribute: .Left, multiplier: 1, constant: 0))
        view.addConstraint(NSLayoutConstraint(item: labels[0], attribute: .Right, relatedBy: .Equal, toItem: spacers[1], attribute: .Left, multiplier: 1, constant: 0))
        view.addConstraint(NSLayoutConstraint(item: spacers[1], attribute: .Right, relatedBy: .Equal, toItem: labels[1], attribute: .Left, multiplier: 1, constant: 0))
        view.addConstraint(NSLayoutConstraint(item: labels[1], attribute: .Right, relatedBy: .Equal, toItem: spacers[2], attribute: .Left, multiplier: 1, constant: 0))
        view.addConstraint(NSLayoutConstraint(item: spacers[2], attribute: .Right, relatedBy: .Equal, toItem: labels[2], attribute: .Left, multiplier: 1, constant: 0))
        view.addConstraint(NSLayoutConstraint(item: labels[2], attribute: .Right, relatedBy: .Equal, toItem: spacers[3], attribute: .Left, multiplier: 1, constant: 0))
        view.addConstraint(NSLayoutConstraint(item: spacers[3], attribute: .Right, relatedBy: .Equal, toItem: view, attribute: .Right, multiplier: 1, constant: 0))

        return view
    }
    else {
        return nil
    }
}

extension Array {
    func pairs(block: (Element, Element?)->()) {
        if count == 0 { return }
        if count == 1 { block(self.first!, nil) }

        var last = self[0]
        for i in self[1..<count] {
            block(last, i)
            last = i
        }
    }
}

This is the result:

Not at all what I was expecting, right?

Now, on to the second method. Instead of posting a bunch of screenshots from Interface Builder, I have created a sample project available here specifically to test this problem. If you open it, the file FooterView.xib contains the footer view constructed in IB that, as far as I know, has exactly the same view structure and auto-layout constraints.

Using that view, like this:

return (NSBundle.mainBundle().loadNibNamed("FooterView", owner: self, options: nil).first as UIView)

yields the result you saw in the first screenshot, which is exactly what I want.

So, with Interface Builder the constraints work as expected. Why doesn't it work when the views & constraints are created in code? What am I missing?