Question

我试图用两个参数定义一个Swift闭包，但是它抛出编译错误。我在做什么错了？

     var processor: (CMSampleBuffer, CVPixelBuffer) throws -> Void { (sampleBuffer, outputPixelBuffer) in

    ....

}

编辑：缺少=，已在注释中正确指出。但是现在，我试图将此闭包作为参数传递，并且在声明中给出了编译错误：

  func process(_ processor: ((_ sampleBuffer: CMSampleBuffer,  toPixelBuffer:CVPixelBuffer) throws)? = nil) {


 }

Answer 1

因此，以下代码似乎在Playground中传递：

func process(_ processor: ((String, String))? = nil) {

}

我很确定主要问题是您想强制使用throws作为关键字。我认为这不可能，我宁愿建议使用看起来像这样的Result enum模式：

enum ProcessResult {
    case success(someReturnValue: YourType) // Or no associated value if you just want to know it worked
    case failed(anError: Error)
}

通过要求代码块返回ProcessResult，您可以强制执行可能在其他语言中使用try / catch的功能。

Answer 2

Function Type needs to be written in this syntax:

( ArgumentList ) throws -> ResultType

(Simplified, you can find a full description in the link above.)

The keyword throws is optional according to your requirement, but -> ResultType is required even if the ResultType is Void.

And ArgumentList cannot have parameter labels, you need to use _ as parameter label when you want to show parameter names for readability.

So, your process(_:) should be something like this:

func process(_ processor: ((_ sampleBuffer: CMSampleBuffer,  _ toPixelBuffer: CVPixelBuffer) throws -> Void)? = nil) {
    //...
}

Or else, if you define a typealias for the parameter type, you can rewrite it as follows:

typealias ProcessorType = (_ sampleBuffer: CMSampleBuffer,  _ toPixelBuffer: CVPixelBuffer) throws -> Void

func process(_ processor: ProcessorType? = nil) {
    //...
}

One more, when you ask something about compilation errors, it is strongly recommended to show whole error message.

You can find a copyable text through the Report Navigator in the Navigator pane (in the Left side of Xcode).

快速关闭多个参数

2 个答案: