   let innerLayoutGuide = UILayoutGuide()
   var merged: [Range<Int>] = []
 
-  private weak var gridView: GridView?
-
   init(gridView: GridView) {
     self.gridView = gridView
   }

// TODO: Swift 3 naming convention
// TODO: update defaults to NSGridView defaults (rowSpacing = 6)
// TODO: fix runtime ambiguous position and size
// TODO: GridRow & GridColumnd .gridView should be public
// TODO: make UIView.animate possible, by not using updateGrid()

public class GridView: UIView {

// MARK: - GridColumn

public class GridColumn {
  public weak var gridView: GridView?
  public var leadingPadding: CGFloat = 0 { didSet { gridView?.updateGrid() } }
  public var trailingPadding: CGFloat = 0 { didSet { gridView?.updateGrid() } }
  // Note: NSGridColumn uses a non-optional CGFloat.leastNormalMagnitude as default
