how to autocomplete library class function in Xcode

Question

Hi, I am new to Xcode.

I am writing a C++ command line project. I used to use netbean. For example if I use a string, then I should be able to invoke the string library API function in a popup list for me to choose to autocomplete. So now I don't know how to do that in Xbox. Can some one help? My question is specific: how to find out the library function API?

Thanks.