swift3 - Nil 与预期的参数类型 Optional 不兼容

Question

我只是将我的 iOS 应用程序的代码更新为 Swift 3，这行代码让我很困惑:

let dataProvider:CGDataProvider? = CGDataProviderCreateWithData(nil, maskImagePixelData!, maskImagePixelData!.count, nil)

这在我使用的先前版本的 Swift 中有效，现在它抛出此错误:

Nil is not compatible with expected argument type 'CGDataProviderReleaseDataCallback' (aka '@convention(c) (Optional<UnsafeMutableRawPointer>, UnsafeRawPointer, Int) -> {}')

我找不到 CGDataProviderCreateWithData 的文档(!) 但签名也让我感到困惑:

CG_EXTERN CGDataProviderRef __nullable CGDataProviderCreateWithData(
    void * __nullable info, const void * cg_nullable data, size_t size,
    CGDataProviderReleaseDataCallback cg_nullable releaseData)

nil 是否有简单的替代品？还是我需要搬进某种 UnsafeMutableRawPointer ?

Answer 1

知道了:

    let releaseMaskImagePixelData: CGDataProviderReleaseDataCallback = { (info: UnsafeMutableRawPointer?, data: UnsafeRawPointer, size: Int) -> () in
        // https://developer.apple.com/reference/coregraphics/cgdataproviderreleasedatacallback
        // N.B. 'CGDataProviderRelease' is unavailable: Core Foundation objects are automatically memory managed
        return
    }
    var dataProvider:CGDataProvider? = CGDataProvider(dataInfo: nil, data: maskImagePixelData!, size: maskImagePixelData!.count, releaseData: releaseMaskImagePixelData)

并与 CGDataProvider.init更换 CGDataProviderCreateWithData文档是 here