swift - segue中数据丢失(xcode8.0)

Question

我是 swift 的初学者，尝试开发显示 BLE 特性的简单程序。我通过打印确认我捕获了目标特征的 UUID

myCharacteristicUUID_1 : (
    "Manufacturer Name String",
    "Model Number String",
    "Serial Number String",
    "Hardware Revision String",
    "Firmware Revision String",
    "Software Revision String"
)

但是，在 override func prepare(for segue: UIStoryboardSegue, sender: Any?),我再次通过打印检查，发现数据消失了，如下所示；

myCharacteristicUUID_2 : (
)

我可以移交其他类型的值(例如字符串、文本等)，但我无法处理从 BLE 捕获的数据。有人能指出当我在 segue 中使用来自 BLE 的数据时我必须做什么吗？下面是我的代码；

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor targetService: CBService, error: Error?) {

    if error != nil {
        print("Characteristic NOT found : \(error)")

    }

    let foundCharacteristics = targetService.characteristics

    for c in foundCharacteristics! as [CBCharacteristic] {

        myCharacteristicUUID.add(c.uuid)

    }

    print("myCharacteristicUUID_1 : \(myCharacteristicUUID)")

}

// prepare for segue
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    if (segue.identifier == "mySegue") {

        print("myCharacteristicUUID_2 : \(myCharacteristicUUID)")

        let mySecondViewController : SecondViewController = segue.destination as! SecondViewController

        mySecondViewController.relayedFoundCharacteristicUUID = myCharacteristicUUID

     }

}

Answer 1

这就是 myCharacterisitcUUID 未正确读取的原因。请查看performSegue的位置。

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

    selectedService = myService[indexPath.row] as! CBService
    print("Selected_service : \(selectedService)")

    self.peripheral.discoverCharacteristics(nil, for:selectedService as CBService!)

    //performSegue(withIdentifier: "mySegue", sender: nil)
    // I used to performed segue here. This was the reason myCharacterisitcUUID was empty.


}

// find the characteristics for the targetService

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor targetService: CBService, error: Error?) {

    if error != nil {
        print("Characteristic NOT found : \(error)")

    }

    foundCharacteristics = targetService.characteristics!

    for c in foundCharacteristics as [CBCharacteristic] {

        self.myCharacteristicUUID.add(c.uuid)

    }
    // segue should be performed here ! This change worked!
    performSegue(withIdentifier: "mySegue", sender: nil)
}