Apple Swift: Type Casting Generics

Question

I\'m writing some Swift code where I have an array containing a generic type:

let _data: Array = T[]()

Later in my code I need to

Answer 1

In swift, as operator is something like dynamic_cast in C++, which can be used to down cast an object.

Say you have an object a of type A, and you can write let a as B only when type B is identical to type A, or B is a sub-class of A.

In your case, apparently Array cannot always be down cast to Array or Array, so compiler reports errors.

A simple fix is to convert to AnyObject first, and then downcast to Array or Array:

let anyData: AnyObject = self._data;
switch anyData {
case let doubleData as? Array: // use as? operator, instead of as,
                                       // to avoid runtime exception
  // Do something with doubleData
case let floatData as? Array:
  // Do something with floatData
default:
  return nil // If the data type is unknown return nil