Swift: check if generic type conforms to protocol

Question

I have a protocol that I defined like so:

protocol MyProtocol {    ... } 

I also have a generic struct:

struct MyStruct <T>  {     ... } 

Finally I have a generic function:

func myFunc <T> (s: MyStruct<T>) -> T? {    ... } 

I'd like to test inside of the function if the type T conforms to MyProtocol. Essentially I'd like to be able to do (~ pseudocode):

let conforms = T.self is MyProtocol 

But this throws a compiler error:

error: cannot downcast from 'T.Type' to non-@objc protocol type 'MyProtocol'    let conforms = T.self is MyProtocol                   ~~~~~~ ^  ~~~~~~~~~~ 

I have also tried variations, like T.self is MyProtocol.self, T is MyProtocol, and using == instead of is. So far I haven't gotten anywhere. Any ideas?

Answer 1

I have to say @Alex want to check if T type conforms to protocol rather than s. And some answerer didn't see clearly.

Check T type conforms to protocol like this :

if let _ = T.self as? MyProtocol.Type {     //  T conform MyProtocol } 

or

if T.self is MyProtocol.Type {     //  T conform MyProtocol } 

Answer 2

A bit late but you can test if something responds to protocol with as ? test:

if let currentVC = myViewController as? MyCustomProtocol {     // currentVC responds to the MyCustomProtocol protocol =] } 

EDIT: a bit shorter:

if let _ = self as? MyProtocol {     // match } 

And using a guard:

guard let _ = self as? MyProtocol else {     // doesn't match     return }