Swift === with nil

Question

Why does the following not work in Swift?

if someObject === nil {
}

You have to do the test using the == operator such as

if someObject == nil {
}

I was thinking that === was more like making sure the instances where the exact same (basically comparing the pointers) and == was more like an isEqual check. Thus I would think === would be more appropriate for testing against nil, but I am obviously incorrect.

The documentation states:

=== or “Identical to” means that two constants or variables of class type refer to exactly the same class instance.

== or “Equal to” means that two instances are considered “equal” or “equivalent” in value, for some appropriate meaning of “equal”, as defined by the type’s designer.”

Answer 1

It works exactly like you expect:

var s: String? = nil
s === nil // true

The only caveat is that to compare to nil, your variable must able to be nil. This means that it must be an optional, denoted with a ?.

var s: String is not allowed to be nil, so would therefore always returns false when === compared to nil.