Formatter data on OS X

[thierryH91200]

if i write

   let data = PieChartData()
    data.addDataSet(dataSet)

   let pFormatter = NumberFormatter()
    pFormatter.numberStyle = .percent
    pFormatter.maximumFractionDigits = 1
    pFormatter.multiplier = 1.0
    pFormatter.percentSymbol = " %"
    data.setValueFormatter(pFormatter )

i have an error
Cannot convert value of type 'NumberFormatter' to expected argument type 'IValueFormatter?'
Xcode offers

     data.setValueFormatter(pFormatter as! IValueFormatter )

and now the program crash

[thierryH91200]

problem solved

    data.setValueFormatter(DefaultValueFormatter(formatter : pFormatter  ))