Have a look at the strings used in an app.
This is not really decompiling, but it can get you some useful info about what strings are visible in an app. If the app has been distributed via the Apple appstore, the binary will have been encrypted. For decryption try Google, this post is only meant to give you insight in what strings are visible in you own binary.
The OSX command line tool “strings” can get you all the strings that are in an app. To do this open a “Terminal” in OSX and type:
This will get you all the strings. Probably this is to much info. Filter it with a grep combination to get to the strings you are interested in. If you are interested in the HTTP connections the app makes, the following command line would do the trick:
strings myapp.app/myapp | grep http
This will get you all strings that contain “http”, and therefore probably all http connections the app makes 🙂