Snooping on iOS API calls?

I'd like to see what kinds of API开发者_开发技巧/framework calls are being made by an arbitrary iOS app. Is there some sort of mechanism or tool that I can use to do this?

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For clarification, the term you are looking for is hooking. It can be easily be done on a Windows system.

Excerpt from Wikipedia: ptrace is a system call found in several Unix and Unix-like operating systems.

Given the design of iOS running one app at a time, I don't believe you can do this. Plus your app will be running in a sandbox environment with each app having it's own virtual address space.