Check for value or reference type in Swift

Question

How can we check if a parameter passed in a function is a value or a reference type? For example

func isReferenceType(toTest: Any) {
    return true // or false
}

As we see here, we are not able to do this leveraging generics.

Itemized

I haven't tried, but doesn't solution no. 2 in the link that you posted work for you? – Godbey

What about is AnyObject? – Whippletree

For Swift 3 and Xcode 8 - https://mcmap.net/q/455613/-anyobject-not-working-in-xcode8-beta6 – Charissacharisse

Answer 1

AnyObject is a protocol that any class type automatically conforms to, so you can write:

func isReferenceType(toTest: Any) -> Bool {
    return toTest.dynamicType is AnyObject
}

class Foo { }
struct Bar { }

isReferenceType(Foo())    // true
isReferenceType(Bar())    // false
isReferenceType("foo")    // false
isReferenceType(123)      // false
isReferenceType([1,2,3])  // false

Circumgyration

Yes, but isReferenceType("foo") or isReferenceType(123) or isReferenceType([1, 2, 3]) will also return true (if Foundation is imported). – Banda

Ah, the old silent cast. Checking the dynamic type instead of the value itself seems to resolve that... – Circumgyration

Or alternatively: func isReferenceType<T: Any>(toTest: T) -> Bool { return !(T.self is AnyObject) } – Itemized

Answer 2

Swift 5

func isReferenceType(_ toTest: Any) -> Bool {
    return type(of: toTest) is AnyClass
}

Irishman