How to make global variable from output socket connection - objective-c

Question

I'd like to create global variable that will contain answers from socket connection.
This is my code:
- (void)initNetworkCommunication {
CFReadStreamRef readStream;
CFWriteStreamRef writeStream;
CFStreamCreatePairWithSocketToHost(NULL, (CFStringRef)#"192.168.0.10", 35000, &readStream, &writeStream);
self.inputStream = objc_unretainedObject(readStream);
self.outputStream = objc_unretainedObject(writeStream);
[self.inputStream setDelegate:self];
[self.outputStream setDelegate:self];
[self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[self.inputStream open];
[self.outputStream open];
}
-(void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
switch (eventCode) {
case NSStreamEventOpenCompleted:
NSLog(#"Połączono\n");
break;
case NSStreamEventHasBytesAvailable:
if (aStream == self.inputStream) {
uint8_t buffer[1024];
long len;
while ([self.inputStream hasBytesAvailable]) {
len = [self.inputStream read:buffer maxLength:sizeof(buffer)];
if (len > 0) {
NSString *output = [[NSString alloc] initWithBytes:buffer length:len encoding:NSASCIIStringEncoding];
if (nil != output) {
NSLog(#"%#",output);
}
}
}
}
break;
case NSStreamEventErrorOccurred:
NSLog(#"Nie można połączyć\n");
break;
case NSStreamEventEndEncountered:
break;
default:
break;
}
}
I want to make output variable as global so I can use it in other functions. I want to do this because I'd like to create conditions - everytime when I send request, controller answers me and sends ">" symbol so that means it is ready to take another request. I want to create condition that will send only when ">" appears. I have already done RegExp for this but now I have problem with access to output variable outside stream function.

Answer 1

When you declaring something as extern you are telling the compiler the type AND that you will define it somewhere else. In your case you never define your variable.
First, ensure it is defined:
// in .h you would have:
extern NSString* const output; // << declaration
// in .m you would have:
NSString * const output = [[NSString alloc] initWithBytes:buffer length:len encoding:NSASCIIStringEncoding]; // << definition