I mean if I write something in the code:
NSString *myKey = @"this is my private key";
Will someone be able to trace back the string "this is my private key" from the IPA?
I ask this for the encryption in iPhone.
If I store my encrypt key in the code, is it already safe? or how should I do it?
Yes, it's likely. An IPA is just a zip file. You can extract it to get the application binary. You can usually run strings over an application binary to see string literals.
来源：https://stackoverflow.com/questions/6305808/is-it-possible-to-trace-back-a-string-inside-an-ipa-binary