swift - 为什么这有效？ Swift(UnsafeMutablePointer<可选>)

Question

protocol Property {}
protocol OptionalProtpery : Property {
        static func codeNilInto(pointer: UnsafePointer<Int>)
    }

    extension Optional : OptionalProtpery {
        static func codeNilInto(pointer: UnsafePointer<Int>) {
            (UnsafeMutablePointer(pointer) as UnsafeMutablePointer<Optional>).memory = nil
        }
    }

我对此声明感兴趣 UnsafeMutablePointer<"Optional">为什么我们没有错误，例如:“可选泛型类型并且需要参数 <...>”。由于此处未指定特定类型(例如 UnsafeMutablePointer<"Optional"<"Int">>)。

Answer 1

protocol Property {}
protocol OptionalProtpery : Property {
    static func codeNilInto(pointer: UnsafePointer<Int>)
}

extension Optional : OptionalProtpery {
    static func codeNilInto(pointer: UnsafePointer<Int>) {
        (UnsafeMutablePointer(pointer) as UnsafeMutablePointer<Optional>).memory = nil
    }
}

var i = 1
let p = withUnsafePointer(&i) { (p) -> UnsafePointer<Int> in
    return p
}
print(p.memory) // 1

//Optional.codeNilInto(p) // error: generic parameter 'Wrapped' could not be inferred
// you have to specify generic parameter !!!
Optional<Int>.codeNilInto(p)
Optional<Double>.codeNilIntro(p)
// or what ever you want to express

所以，因为Optional是通用的，所以你的代码是“OK”。顺便问一下，您希望您的代码做什么？