receive Data via BLE on IOS, Data is always old - ios

Question

I´m new in iOS Programming and i´m trying to receive Data from a BLE device. I´m able to connect to the device and send data to the device. The problem is receiving data from the BLE Device.
Im using this as BLE Base:
LGBluetooth
Problem:
#property (nonatomic,strong) NSString* recievedData; //data recieved from Peripheral
- (void)RecieveDataBLE:(LGPeripheral *)peripheral :(NSString*)Service_UUID :(NSString*)Characteristic_UUID {
//Function to read Data from BLE Device
[LGUtils readDataFromCharactUUID:Characteristic_UUID serviceUUID:Service_UUID
peripheral:peripheral
completion:^(NSData *data, NSError *error) {
NSLog(#"Data : %s Error : %#", (char *)[data bytes], error);
recievedData = [NSString stringWithUTF8String:[data bytes]];
}
- (IBAction)sendDOWN:(id)sender {
MessageLabel.hidden = NO;
[self RecieveDataBLE:mBuddy:SERVICE_UUID_DEVICE_INFORMATION:CHARACTERISTIC_UUID_MANUFACTURER];
MessageLabel.text = [NSString stringWithFormat:#"%#",recievedData]; //Output is always old!!
}
After the action sendDown is called, data should be read via the ReceiveDataBle function. This one will then process the data. The problem is, ReceiveDataBle is always too late, and does not receive the information immediately, but after a certain time. A callback function returns the data to ReceiveDataBle. So when the action SendDown is called the Data from the last call appears in the MessageLabel!!
The question is, how can I ensure that I have the newest data available, and not outdated data?

Answer 1

**You can use this type when show updated recievedData **
-(IBAction)sendDOWN:(id)sender
{
MessageLabel.hidden = NO;
[LGUtils readDataFromCharactUUID:Characteristic_UUID
serviceUUID:Service_UUID
peripheral:peripheral
completion:^(NSData *data, NSError *error) {
NSLog(#"Data : %s Error : %#", (char *)[data bytes], error);
recievedData = [NSString stringWithUTF8String:[data bytes]];
MessageLabel.text = [NSString stringWithFormat:#"%#",recievedData];
}
}