I download one example from this link. Currently I am using xcode 4.2. It shows AFNetworkReachabilityStatus as undeclared variable. Please give any link to learn AFNetworking.
There are different versions of AFNetworking.
Latest AFNetworking 2.0 and higher requires Xcode 5, targeting either iOS 6.0 and above, or Mac OS 10.8 Mountain Lion (64-bit with modern Cocoa runtime) and above.
For compatibility with iOS 5 or Mac OS X 10.7, use the 1.x release.
For compatibility with iOS 4.3 or Mac OS X 10.6, use the 0.10.x release.
Now if you want to support ios 4.3 or greater use 0.10 release.
来源：https://stackoverflow.com/questions/19517002/can-any-one-please-tell-about-the-use-of-afnetworking-then-it-support-all-xcod