import NumPad
let numPad = NumPad(frame: CGRect(x: 0, y: 0, width: 320, height: 600))
numPad.dataSource = self
numPad.delegate = self
addSubview(numPad)

// number of rows
func numberOfRowsInNumPad(numPad: NumPad) -> Int
// number of columns for row
func numPad(numPad: NumPad, numberOfColumnsInRow row: Row) -> Int
// item for position
func numPad(numPad: NumPad, itemAtPosition position: Position) -> Item

// handle item tap
func numPad(numPad: NumPad, itemTapped item: Item, atPosition position: Position)
// item size for position
func numPad(numPad: NumPad, sizeForItemAtPosition position: Position) -> CGSize