OS X Cocoa Auto Layout hidden elements

Question

I am trying to use the new Auto Layout in Lion because it seems quite nice. But I can not find good information about how to do things. For example:

I have two labels:

Answer 1

Solved this issue programmatically. I have a few buttons in a row, and I may decide to hide one at any time.

Used Cartography to replace them each time hidden changes in any of them.

let buttons = self.buttons!.filter { button in
    return !button.hidden
}

constrain(buttons, replace: self.constraintGroup) { buttons in
    let superview = buttons.first!.superview!

    buttons.first!.left == superview.left

    for var i = 1; i < buttons.count; i++ {
        buttons[i].left == buttons[i-1].right + 10
    }

    buttons.last!.right == superview.right
}