Can we test if objects conforming to the same protocol are identical in swift without casting?

Question

I was trying to test if two objects generated from a factory were identical, but the compiler does not seem to allow identity checking of objects that merely conform to the same protocol. Casting both objects to AnyObject seems fine however. Is there anyway to avoid what seems like unnecessary casting?

Here is a simple example the demonstrates what I am seeing (in swift 1.2)

protocol FooBar {

}

class Foo: FooBar   {

}

class Bar {

  let foo1: FooBar?
  let foo2: FooBar?

  init() {
    foo1 = Foo()
    foo2 = Foo()
    if foo1! as? AnyObject === foo2! as? AnyObject {  // this is fine

    }

    if foo1! === foo2!  {  // Birnary operator '===' cannot be applied to two FooBar operands

    }
  }

}

Answer 1

The identity operator === can only be applied to references, i.e. instances of classes. If all types conforming to the FooBar protocol are classes then you can declare it as a "class protocol"

protocol FooBar : class { }

Then

if foo1! === foo2! { ... }

compiles and works as expected, because the compiler "knows" that both operands are references to a class instance.