value =（null）是什么意思？

Question

<CBService: 0x1702622c0 Peripheral = <CBPeripheral: 0x1780bc680 identifier = 17D7A5C8-BAB5-82E6-826E-BE80A994687A, Name = "Bluegiga CR Demo", state = connected>, Primary = YES, UUID = 0BD51666-E7CB-469B-8E4D-2742F1BA77CC>

Notification began on <CBCharacteristic: 0x170086e50 UUID = E7ADD780-B042-4876-AAE1-112855353CC1, Value = (null), Properties = 0x28, Notifying = YES, Broadcasting = NO>

value =（null）是什么意思？我不能使用writeValue？我需要使用updateValue？

Answer 1

CBCharacteristic有多个@properties ... https://developer.apple.com/library/ios/documentation/CoreBluetooth/Reference/CBCharacteristic_Class/translated_content/CBCharacteristic.html

一个名为value NSData。

如果为null，则表示其中没有数据。它还没有被实例化。