extension Array {
    /**
     Hacky way to may a Array with Type Elemnet to an arry with Supertype T. T must be Supertype of Array.Element

     - returns: array of type T
     */
    func mapType<T>() -> Array<T> {
        let mappedCategorys: Array<T> = self.map { return $0 as! T }

        return mappedCategorys
    }
}

//Usage
protocol Foo {}
struct Bar: Foo {}
let listOfBar = [Bar(), Bar()]
let listOfFoo: Array<Foo> = listOfBar.mapType()