swift - 参数标签错误

Question

转换为 Swift 后获取参数标签错误:
参数标签“(bytes:, length:)”与任何可用的重载都不匹配

关于有效负载分配:
让有效负载=数据(字节:字节，长度:长度)

        if characteristic.uuid.isEqual(CBUUID(string: TRANSFER_CHARACTERISTIC_UUID)) {
            print("Writing to characteristic \(characteristic)")
            let zpl: String = "^XA^FO50,50^ADN,36,20^FDHELLO WORLD^FS^XZ"
            let bytes = zpl.utf8
            let length: size_t = (zpl.characters.count ?? 0)

            let payload = Data(bytes: bytes, length: length)
            print("Writing payload: \(payload) length of \(length)")
            //peripheral.writeValue(payload, forCharacteristic: characteristic, type: CBCharacteristicWriteWithResponse)
            peripheral.writeValue(payload, for: characteristic, type: CBCharacteristicWriteType)
        }

以及以下内容:

textview.text = String(数据, 编码: String.Encoding.utf8)

    if (stringFromData == "EOM") {
        // We have, so show the data,
        textview.text = String(data, encoding: String.Encoding.utf8)
        // Cancel our subscription to the characteristic
        peripheral.setNotifyValue(false, for: characteristic)
        // and disconnect from the peripehral
        centralManager?.cancelPeripheralConnection(peripheral)
    }

建议？

Answer 1

如果您查看文档或在 Xcode 中使用自动完成功能，您将找到该方法的 bytes:count: 版本。也许你想要这样的东西:

let zpl: String = "^XA^FO50,50^ADN,36,20^FDHELLO WORLD^FS^XZ"
var bytes = zpl.utf8

let payload = Data(bytes: &bytes, count: zpl.characters.count)