Usage of where in if let assignment in Swift

Question

The Swift documentation at page 61 of the Swift manual hints to the possibility of using where to join an optional binding with a regular condition. Yet when I do i

Answer 1

In xcode 9

if let str = textField.text as String!, !str.isEmpty
{
   params[key] = str
   TextFieldHelper.setup(textField: textField)
}
else
{ 
   TextFieldHelper.error(textField: textField)
}