Try typing the following code:

#ifndef TEST_H
#define TEST_H

class foo
{
	void bar()
	{
	}
};

void test(foo const& f)
{
	f.
}

#endif // TEST_H

As you type f. QtCreator doesn't offer any auto-completion. In more complex real world code it does offer auto-completion options, but the drop-down menu does not contain the class members. Instead it contains all kinds of C/C++ keywords, fundamental types and pre-defined macros - nothing related to the relevant class.