与Declare @ds TABLE (id int, value int, acc_no int, dt datetime)
INSERT INTO @ds
SELECT 1, 12, 1, '2019-01-01 07:40:38.250' UNION
SELECT 2, 14, 1, '2019-01-02 07:41:05.883' UNION
SELECT 3, 15, 1, '2019-01-13 07:41:22.377' UNION
SELECT 4, 10, 2, '2019-01-14 08:15:53.403' UNION
SELECT 5, 16, 2, '2019-01-03 13:52:47.347' UNION
SELECT 6, 19, 1, '2019-01-09 13:53:56.317' UNION
SELECT 7, 7, 3, '2019-01-17 00:00:00.000' UNION
SELECT 8, 24, 2, '2019-01-17 00:00:00.000' UNION
SELECT 9, 19, 2, '2019-01-02 00:00:00.000' UNION
SELECT 10, 7, 1, '2019-01-07 00:00:00.000' UNION
SELECT 11, 24, 1, '2019-01-05 14:12:47.080' UNION
SELECT 12, 20, 3, '2019-01-28 00:00:00.000'
SELECT id, value, acc_no, dt, value - previous AS result
FROM (
SELECT ROW_NUMBER() OVER (PARTITION BY DS1.id
ORDER BY DS2.dt DESC) AS rn
,DS1.*, COALESCE(DS2.value,0) AS previous
FROM @ds DS1
LEFT JOIN @ds DS2
ON DS2.acc_no = DS1.acc_no
AND DS2.dt < DS1.dt
) AS dt
WHERE rn = 1
一起使用时，读取特性值时，我在CoreBluetooth协议的 peripheral（_：didUpdateValueFor：error：）函数中遇到错误
我一直在调试控制台中收到此消息：
CBPeripheralDelegate我为解决该问题所做的一切尝试都失败了。
有人有这样的经验并找到了解决方案吗？
以下是一些相关代码：
Error in peripheral(_:didUpdateValueFor:error:) :
Error Domain=CBATTErrorDomain Code=6 "The request is not supported."
UserInfo={NSLocalizedDescription=The request is not supported.}
这是外围应用程序中创建特征的代码块：
// CBPeripheralDelegate protocol implementation.
func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
print(#function)
if error != nil {
print("Error in \(#function) :\n\(error!)")
return
}
for service in peripheral.services ?? [] {
print("Discovered service \(service)")
if service.uuid == service_UUID {
peripheral.discoverCharacteristics(nil, for: service)
//peripheral.discoverCharacteristics([svcCharac_UUID], for: service) (Same problem!)
}
}
}
func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor
service: CBService, error: Error?) {
print(#function)
if error != nil {
print("Error in \(#function) :\n\(error!)")
return
}
for characteristic in service.characteristics ?? [] {
print("Discovered characteristic \(characteristic)")
if characteristic.uuid == svcCharac_UUID {
peripheral.setNotifyValue(true, for: characteristic)
peripheral.readValue(for: characteristic)
}
}
}
func peripheral(_ peripheral: CBPeripheral,
didUpdateValueFor characteristic: CBCharacteristic,
error: Error?) {
print(#function)
if error != nil {
print("Error in \(#function) :\n\(error!)")
return
}
.................
}