Picker format

[corbrink]

I'm configuring the picker with array values like this:

`row = FormRowDescriptor(tag: Static.picker, rowType: .Picker, title: "Value")
row.configuration[FormRowDescriptor.Configuration.Options] = array.count
row.configuration[FormRowDescriptor.Configuration.TitleFormatterClosure] = { value in

var stringArray = String
for index in 0...self.array.count {
// append index with cast it to string
stringArray.append(String(index))
}
return stringArray
} as TitleFormatterClosure`

however I get an error
"Cannot convert return expression of type '[String]' to return type 'String!'" Why does this happen?