iOS central writing is not permitted - ios

Question

I am a ios developer.
I can take a value from arduino sensor. But i cannot send a message by using the following the method.
[peripheral writeValue:dataToWrite forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];
"dataToWrite" value is alloc by using NSString*
NSString* data = #"1";
NSData* dataToWrite = [data dataUsingEncoding:NSUTF8StringEncoding];
and the following code is full code of "DiscoverCharacteristics in service"
//DISCOVER CHAR
-(void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
{
if (error) {NSLog(#"DISCOVER_CHAR - Error");return;}
NSString* data = #"1";
NSData* dataToWrite = [data dataUsingEncoding:NSUTF8StringEncoding];
for (CBCharacteristic * characteristic in service.characteristics) {
NSLog(#"DISCOVER_CHAR - Characteristic : %#",characteristic);
[peripheral writeValue:dataToWrite forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];
}
}
In this point, I want to summarize my question.
My Question is
"Even i used the [Peripheral writeValue:forCharacteristic:type] Method. why an error message is shown in log monitor? " Like "Writing is not permitted."
Do i need to get some permission to writing the message for an Arduino?
OR I have to change my following code?
OR I have a problem in Arduino(Acutally, Arduino can get a message from other device... so, Arduino source code is fine. maybe...)
NSString* data = #"1";
NSData* dataToWrite = [data dataUsingEncoding:NSUTF8StringEncoding];
I'm a bit of a bluetooth noob. So it's probably something obvious I've overlooked but any help would be much appreciated.
Thank you!:)

Answer 1

Thank you a lot!!!!!!! Paulw11. Finally, i sent a data from iphone to Arduino. what i checked properties of my characteristic is
<CBCharacteristic: 0x13564a680, UUID = FFE1, properties = 0x16, value = (null), notifying = NO>.
My characteristic's properties = 0x16. but i can not find a 0x16 in enum of properties. Still, I don't know the 0x16 meaning. Someone said that "Values representing the possible properties of a characteristic. Since characteristic properties can be combined, a characteristic may have multiple property values set."
URL: Interpret Characteristic Properties (iOS and BLE) .
Anyway I could find a solution by PaulW11 help! How i can do it? Here is my way of solution.
At first, My method is [peripheral writeValue:dataToWrite forCharacteristic:characteristic *type:CBCharacteristicWriteWithResponse]*;.
The problem code is type field. I had to understand the type. The type has a meaning of write, read and so on. So, I changed the type from CBCharacteristicWriteWithResponse to CBCharacteristicPropertyWrite. That is what i did.
[peripheral writeValue:dataToWrite forCharacteristic:characteristic *type:CBCharacteristicPropertyWrite*];
Thank you again! Paulw11

Answer 2

try to print error inside following method:
-(void)peripheral:(CBPeripheral *)peripheral
didWriteValueForCharacteristic:(CBCharacteristic *)characteristic
error:(NSError *)error
{
NSLog(#"%#",error.localizedDescription);
}
If the error is "Writing is not permitted", then you might not writing the data correctly.Convert the string value in this format
NSData* data = [#"string_to_write" dataUsingEncoding:NSASCIIStringEncoding];
And try this:
[self.peripheral writeValue:data forCharacteristic:self.characteristic type:CBCharacteristicWriteWithoutResponse];
Hope it works!!