How to get the unwrapped type from an optional type in Swift?

Question

I'm trying to get an unwrapped type from an optional type in runtime. The following code would print the type of a as Optional<String>.

class MySubClass: MyClass {

    var a: String? = nil
}

var a = MySubClass()

let mirror = Mirror(reflecting: a)
for child in mirror.children {
    print(child.value.dynamicType)
}

Now I want to unwrap the type and get String, what should I do to make this happen in runtime?

Answer 1

Assuming you have an optional

let someVar: String?

then print(type(of: someVar)) will print

Optional<String>

but if you add the following extension to Optional

protocol OptionalProtocol {
 func wrappedType() -> Any.Type
}

extension Optional: OptionalProtocol {
 func wrappedType() -> Any.Type {
   return Wrapped.self
 }
}

then print(someVar.wrappedType()) will print

String

No reflection whatsoever

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Summary

As long as the optional is not referenced by Any or AnyObject the code will work fine.

For Any you will have to cast it to OptionalProtocol first. Running

let someVar: String?
let anyVar = someVar as Any

if let op = anyVar as? OptionalProtocol {
    print(op.wrappedType())
}

will print

String

As for AnyObject, strangely enough (at least for me), it doesn't cast to OptionalProtocol.

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The original StackOverflow answer can be found here