快速关闭不起作用

Question

我试图运行关闭，但我收到一个错误。无法将类型'（）'的值转换为结束结果类型'Bool'。我不确定我在这里做错了什么。

func runPrintCycle(){ 
     self.runPrinter1() { success in 
      self.runPrinter2() { success in 
       print("Success") 
      } 
     } 
    } 

    func runPrinter1(completionHandler: (Bool) -> Bool){ 
     if let printer1 = Workstation.instance.printer1{ 
      let receiptPrinter = Print(printer: printer1) 
      receiptPrinter.runPrinterReceiptSequence() { success in 
       completionHandler(true) 
      } 
     }else{ 
      completionHandler(true) 
     } 
    } 

func runPrinter2(completionHandler: (Bool) -> Bool){ 
      if let printer2 = Workstation.instance.printer2{ 
       let receiptPrinter = Print(printer: printer2) 
       receiptPrinter.runPrinterReceiptSequence() { success in 
        completionHandler(true) 
       } 
      }else{ 
       completionHandler(true) 
      } 
     } 

Answer 1

你可能不需要声明completeon关闭在runPrinter函数返回值Bool。让他们改为返回Void。当打印机未找到时，您可能还想发送false关闭：

func runPrintCycle() { 
    self.runPrinter1() { success in 
     print("Printer 1: \(success)") 
     // put here if(success) if you wish run second printer only on success 
     self.runPrinter2() { success in 
      print("Printer 2: \(success)") 
     } 
    } 
} 

func runPrinter1(completionHandler: (Bool) ->()) { 
    if let printer1 = Workstation.instance.printer1 { 
     let receiptPrinter = Print(printer: printer1) 
     receiptPrinter.runPrinterReceiptSequence() { success in 
      completionHandler(true) //probably success instead true? 
     } 
    }else{ 
     completionHandler(false) 
    } 
} 

func runPrinter2(completionHandler: (Bool) ->()){ 
    if let printer2 = Workstation.instance.printer2{ 
     let receiptPrinter = Print(printer: printer2) 
     receiptPrinter.runPrinterReceiptSequence() { success in 
      completionHandler(true) //probably success instead true? 
     } 
    }else{ 
     completionHandler(false) 
    } 
}