How to pass a Swift type as a method argument?

Question

I'd like to do something like this:

func doSomething(a: AnyObject, myType: ????) {    if let a = a as? myType    {        //…    } } 

In Objective-C the class of class was Class

Answer 1

You have to use a generic function where the parameter is only used for type information so you cast it to T:

func doSomething<T>(_ a: Any, myType: T.Type) {     if let a = a as? T {         //…     } }  // usage doSomething("Hello World", myType: String.self) 

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Using an initializer of the type T

You don’t know the signature of T in general because T can be any type. So you have to specify the signature in a protocol.

For example:

protocol IntInitializable {     init(value: Int) } 

With this protocol you could then write

func numberFactory<T: IntInitializable>(value: Int, numberType: T.Type) -> T {     return T.init(value: value) }  // usage numberFactory(value: 4, numberType: MyNumber.self)