I am developing for BLE in objective-C.

I define the UUID like the following code:

```
    static NSString *const LEDStateCharacteristicUUID = @"ffffffff-7777-7uj7-a111-d631d00173f4";

```

I want to write characteristic to BLE device by following code , it need to pass 3 parameter:1.Data 2.Characteristic 3.type 

```
CBCharacteristic *chara = ??? // how to set the characteristic via above UUID let it can pass to following function?

[peripheral writeValue:data forCharacteristic:chara type:CBCharacteristicWriteWithoutResponse];

```

How to set the characteristic via above UUID let it can pass to `writeCharacteristic` function?

Thanks in advance.