Getting NSToolbar Height From an NSWindow in Swift

import Cocoa

extension NSWindow {

    func toolbarHeight() -> CGFloat {
        var toolbar: NSToolbar?
        var toolbarHeight = CGFloat(0.0)
        var windowFrame: NSRect

        toolbar = self.toolbar

        if let toolbar = toolbar {
            if toolbar.visible {
                windowFrame = NSWindow.contentRectForFrameRect(self.frame, styleMask: self.styleMask)
                toolbarHeight = NSHeight(windowFrame) - NSHeight(self.contentView.frame)
            }
        }

        return toolbarHeight
    }
}