std::vector access violation

I'm new to the std vector class, and recently implimented a class structure similar to the one in the program below. When I received an "Access Violation" error when trying to push something into the vector, I recreated the problem in a simpler program (show below). I'm assuming that the vector has no room to grow within a structure and causing an error message, but am not sure how the vector actually works. If that is the case, I would greatly appreciate a suggestion on how to use an alternative method of achieving a similar system using the vector class. I'm hoping that I'm just using it wrong though.

Code:

---

#include <vector>

using namespace std;

struct s{
        vector<int> v;
};
int main(){
        vector<s> db;
        s ns;
        db.push_back(ns);
        s *p = db.end();
        p->v.push_back(4);
        return 0;
}

---

please help me! :(

db.end() returns an iterator, not a vector element.

look at this: http://www.sgi.com/tech/stl/Vector.html

I'm glad i'm seeing this thread 'cause i'm about to start an intensive study on the vector class. :)

std::vector.end() returns an iterator to the element AFTER the last element. Use db[db.size() - 1].v.push_back(4) or something instead?

I think you want the back() method which returns a reference to the last element:

Code:

---

        s& lastItem = db.back();
        lastItem.v.push_back(4);

---

make p vector<s>::iterator and assign it the value of db.end(). Decrement the value of p by 1. Use the arrow operator on p to get the last element of v, which can be obtained using the back() method of vectors.


vector<s>::iterator p = db.end();
--p;
cout << p->v.back();