- (void)performSelector:(SEL)aSelector withContext:(void*)context,... {
	if (context) {
		NSMethodSignature *signature = [self methodSignatureForSelector:aSelector];
		NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
		[invocation retainArguments];
		
		NSUInteger argumentCount = [signature numberOfArguments] - 2;
		
		[invocation setTarget:self];			// index 0
		[invocation setSelector:aSelector];	    // index 1
		
		va_list arguments;
		
		va_start(arguments, context);
		
		// 인자의 개수는 +2가 된 상태 
		NSUInteger i, count = argumentCount;
		void *currentValue = context;
		
		for (i = 0; i < count; i++) {
			[invocation setArgument:¤tValue atIndex:(i + 2)];
			currentValue = va_arg(arguments, void*); // 다음 인자 읽기 
		}
		
		va_end(arguments);
		
		NSThread *customWorkerThread = [NSThread currentThread];
		
		[invocation performSelector:@selector(invoke) onThread:customWorkerThread withObject:nil waitUntilDone:NO];
		
	} else {
		[self performSelectorInBackground:aSelector withObject:nil];
        
	}
}

// 호출할 메서드 
- (void)printArgument:(NSString*)arg1 andOther:(NSString*)arg2 andAnother:(NSString*)arg3 {
	NSLog(@"%@", [NSThread currentThread]);  
	NSLog(@"arg1: %@", arg1);
	NSLog(@"arg2: %@", arg2);
	NSLog(@"arg3: %@", arg3);
}

// 요렇게 호출할 수 있다. 깔끔하지 않는가? 
[self performSelector:@selector(printArgument:andOther:andAnother:) withContext:@"t1", @"t2", @"t3", nil];