一个swift例子

··· class C { required init() {}

func f() {
    print("Hello from C")
}

}

extension Array where Element: C { init(num: Int) { self.init() for _ in 0..<num { self.append(Element()) } }

func callFOnEverything() {
    for obj in self {
        obj.f()
    }
}

}

Array (num: 4).callFOnEverything()

···