Dereferencing iterator to pointers correctly - c++

Question

I have a vector of pointers to objects. Each object stores a value and has a toString() function that returns that value as a string. I have an iterator to go through the vector and I need to extract the value of each object by calling toString(). The problem is, I can't figure out how to get the value.
This function is ultimately supposed to write the number to a file, but I'm using the cout for testing.
void writeNumbers(vector<Integer*>& input)
{
ofstream write;
write.open("Integers.txt");
vector<Integer*>::iterator iter = input.begin();
for (iter; iter < input.end(); iter++)
{
**std::cout << (*iter)->toString() << std::endl;**
}
write.close();
I get an Access Violation error which points me to the toString() function:
std::string Integer::toString()
{
std::stringstream ss;
ss << *(this)->value;
return ss.str();
}
toString() works fine whenever I don't try to access it through the iterator.
Edit: Value in toString is actually a pointer to a number.
Edit2: New writeNumbers:
void writeNumbers(vector<Integer*>& input)
{
ofstream write;
write.open("Integers.txt");
vector<Integer*>::iterator iter = input.begin();
for (iter; iter != input.end(); iter++)
{
std::cout << (*iter)->toString() << std::endl;
}
write.close();
}
Final Edit: Alright, the problem turned out to be a borked constructor that was failing to initialize a pointer properly, so I was WAY off base on where the problem actually was. :)
Integer::Integer(string input)
{
if(isNaN(input))
value = new int(atoi(input.c_str()));
}
So it should have been !isNaN, plus I fixed the problem of initializing it on bad input:
//New constructor, works 100%
Integer::Integer(string input)
{
if(!isNaN(input))
value = new int(atoi(input.c_str()));
else
value = new int(0);
}

Answer 1

Your toSting() has the issue. Change
ss <<*(this)->value;
to
ss << value;

Answer 2

EDIT: This is not an error, but a general advice when using iterators. Dont use < to check for end, use !=.
iter < input.end()
It should be like this:
iter != input.end()
This is because for certain containers, the < operator will not do what you expect. As a result, at some point you could be dereferencing input.end() itself, which points at nothing.