ios - 在闭包中获取变量是否完整？

Question

我有一个创建 PDF 文件的闭包函数 - 这可能需要一些时间，并且包含一个进度函数。我的问题是，我如何在关闭之外收到“进度”？

例如:

func makeReport(fileName:String, task: Task, completion:@escaping (_ success:Bool) -> Void) {
    .....
    let _ = pdf.generatePDF(fileName, progress: {
        progress in
        print(progress) // here is my progress
    })

    completion(true) // returns when the file is created, so i know that i am now able to show the PDF
}

我用以下方式调用我的函数:

pdfCreator.makeReport(fileName: filename, task: self.task, completion: {success in
   // any chance to get my progress to update a spinner for example?
   if success == true {
       // file is here
   }
}

Answer 1

这是一个使用 Playground 的基本示例，应该可以帮助您:

func makeReport(fileName: String, progress: @escaping (_ progress: CGFloat) -> Void, completion: @escaping (_ success: Bool) -> Void) {

  var progressOfTask: CGFloat = 0.0
  let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { (timer) in
        progressOfTask += 10
        progress(progressOfTask)
        if progressOfTask == 100.0 {
            completion(true)
            timer.invalidate()
        }
    }
    timer.fire()
}


makeReport(fileName: "", progress: { progress in
    print(progress)
}, completion: { success in
    print(success)
})

PlaygroundPage.current.needsIndefiniteExecution = true

输出:

10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
true