Well, after checking this issue Memory related issue of ZBarReaderViewController in iOS 7, I did manage to solve the problem. The lines I've added are the following:
(in my viewcontroller.h)
@property (strong,nonatomic) ZBarReaderViewController *reader;
(in my viewcontroller.m)
if(self.reader)
{
[self.reader.readerView stop];
for(UIView *subViews in self.reader.view.subviews)
[subViews removeFromSuperview];
[self.reader.view removeFromSuperview];
self.reader.view = nil;
}
_reader = [ZBarReaderViewController new];