Matrix questions

• linkedin connect API gives error 401 - iphone
• Why don't we make every property of class thread safe normally?
• How current queue, dispatch queue and target queue communicates with each other in GCD?
• 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?

Matrix answers