Thread: dereferencing vector iterators

I want to dereference a vector iterator that points to a vector of class objects whose members are pointers. I'm using a compound class (class 1) whose members are pointers to another class (class 2). Class 2 has an int member variable, which I want to retrieve. If I retrieve the variable using array indexing, everything works fine. But when I try to dereference the iterator, I get a compiler error (gcc version 4.0.1 (Apple Inc. build 5465).

Here is the code (example.cpp):

Code:

//example.cpp
#include <iostream>
#include <vector>
using namespace std;

class Class1{
	public:
		Class1() : num(10) { /***/ }
		int num;
		int get_num() { return num; }
};

class Class2{
	public:
		Class2(Class1* C1obj) : C1ptr(C1obj) { /***/ }
		Class1* C1ptr;
		Class1* get_C1ptr() { return C1ptr; }
};

int main() {
   int i;
   Class1* C1p;  //pointer to objects of class Class1
   Class2* C2p;  //pointer to objects of class Class2
   vector<Class1> C1v(5); //vector of 5 Class1 objects (calls constructor)
   vector<Class2*> C2v;   //empty vector of pointers to Class2 objects
   vector<Class2*>::iterator p;

   //fill empty vector of type Class2 with pointers to objects whose members are of type Class1
   for(i = 0; i < 5; i++) {
	C1p = &C1v[i];        
	C2p = new Class2(C1p);
	C2v.push_back(C2p);
   }

   //THIS WORKS PROPERLY
   for(i = 0; i < 5; i++) {
	cout << data[i]->get_C1ptr()->get_num() << endl;
   }

   //THIS CAUSES ERROR
   for(p = data.begin(); p != data.end(); ++p) {
	cout << *p->get_C1ptr()->get_num() << endl;
   }

   return 0;
}

Error message (I've tagged this as code to keep out the smileys caused by punctuation):

Code:

example.cpp: In function ‘int main()’:
example.cpp:37: error: request for member ‘get_C1ptr’ in ‘* p. __gnu_cxx::__normal_iterator<_Iterator, _Container>::operator->
  [with _Iterator = Class2**, _Container = std::vector<Class2*, std::allocator<Class2*> >]()’, which is of non-class type ‘Class2*’

I could use the array indexing, but I want to understand why the iterator doesn't work. What's the proper way to dereference the iterator here?
Mike

What is data?

The problem might be that *p->get_C1ptr()->get_num() is *(p->get_C1ptr()->get_num()), so you might want to write it as (*p)->get_C1ptr()->get_num().