Matrix questions

• when should we use semaphore vs dispatch group vs operation queue?
• Can someone explain File Owner in iOS [duplicate]
• If two different Categories having same method, then which one will be invoked by Objective C runtime system?
• Face Recognition Logic
• what is the difference between strong (in LLVM) and retain( in GCC)?
• Reading Data from UIWebView
• Is function overloading possible in Objective C?
• How do I measure the distance traveled by an iPhone using the accelerometer?
• Custom pin animation - MKMapView
• How can i get Original order of NSDictionary/NSMutableDictionary?

Matrix answers