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swift - Check if variable is an Optional, and what type it wraps

Is it possible to check if a variable is an optional, and what type is it wrapping?

It is possible to check if a variable is an specific optional:

let someString: String? = "oneString"
var anyThing: Any = someString

anyThing.dynamicType // Swift.Optional<Swift.String>
anyThing.dynamicType is Optional<String>.Type // true
anyThing.dynamicType is Optional<UIView>.Type // false

But is it possible to check agains any type of optional? Something like:

anyThing.dynamicType is Optional.Type // fails since T cant be inferred
// or 
anyThing.dynamicType is Optional<Any>.Type // false

And once knowing you have an optional, retrieve the type it is wrapping:

// hypothetical code 
anyThing.optionalType // returns String.Type
See Question&Answers more detail:os

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Since a protocol can be created as means of a typeless Optional the same protocol can be used to provide access to the optional type. Example is in Swift 2, although it should work similarly in previous versions:

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

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

let maybeInt: Any = Optional<Int>.Some(12)
let maybeString: Any = Optional<String>.Some("maybe")

if let optional = maybeInt as? OptionalProtocol {
    print(optional.wrappedType()) // Int
    optional.wrappedType() is Int.Type // true
}

if let optional = maybeString as? OptionalProtocol {
    print(optional.wrappedType()) // String
    optional.wrappedType() is String.Type // true
}

The protocol can even be used to check and unwrap the contained optional value


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