how to know if current architecture is i386 or x86_64 in macs? (Xcode)

Question

I am handling a camera that needs different parameters in different architecture, Is there a flag that I can check to see if I am in 32bits or 64bits in my mac? I was trying

Answer 1

#ifdef __LP64__
// 64-bit code
#else
// 32-bit code
#endif

Source: http://developer.apple.com/mac/library/documentation/Darwin/Conceptual/64bitPorting/MakingCode64-BitClean/MakingCode64-BitClean.html#//apple_ref/doc/uid/TP40001064-CH226-SW2