Q:

Extend super class that match Generics? 

I want to use Generics in super class, but when I create child class, I got error
reference to generic type 'A' requires arguments in <...>

How to define Child Class B? 
import UIKit
import Foundation

var str = "Hello, playground"

protocol MyProtocol{
    func protocolfunc()
}

class A <T:MyProtocol> {

}
class B :A{
}

A:

If B is supposed to be generic itself:
class B<T:MyProtocol> : A<T> { ... }

If B is not supposed to be generic then:
class SomeType : MyProtocol { ... }
class B : A<SomeType> { ... }

For example:
Welcome to Apple Swift version 2.1 (700.1.101.6 700.1.76).  Type :help for assistance. 
  1> class A<T> {}
  2> class B : A<Int> {}
  3>  
  4> class B<T> : A<T> {}

