I need a way to have a pointer permanently point to an element in a std::vector. Using a pointer to an element works fine, until another element is added, as demonstrated by the following code:
[cpp]#include <iostream>
#include <vector>
int main( )
{
std::vector<int> numbers;
numbers.push_back( 1337 );
std::vector<int>::pointer pfn = &numbers[0];
std::cout << "pfn -> " << pfn << " : " << *pfn << std::endl;
numbers.push_back( 1234 );
std::cout << "pfn -> " << pfn << " : " << *pfn << std::endl;
std::cin.get( );
return 0;
}[/cpp]
The output is:
[code]pfn -> 003469C8 : 1337
pfn -> 003469C8 : -17891602[/code]
I understand that when working with arrays it's not possible to keep an element at the same memory address when resizing, so how should I solve this? I could store an integer with the index at which the element resides, but I really need a function to return a pointer, so the element can be modified. The problem is that other elements will be created, but elements other than the last one still need to be modified.
Three options:
1) don't do that
2) use a vector of integer pointers, that way you can pass stuff the actual heap-allocated memory address of the int, and the vector will only mess with the address of the pointers
3) use an std::list
Awesome. Now, is there any shorter way to do the code between the equal signs?
[cpp]#include <iostream>
#include <list>
int main( )
{
std::list<int> numbers;
numbers.push_back( 1 );
numbers.push_back( 2 );
numbers.push_back( 3 );
// =============================================================================
std::list<int>::iterator it = numbers.begin( );
it++;
int* pfn = &*it;
// =============================================================================
std::cin.get( );
return 0;
}[/cpp]
The following didn't work by the way:
[cpp]int* pfn = (int*)it;[/cpp]
[code]error C2440: 'type cast' : cannot convert from 'std::list<_Ty>::_Iterator<_Secure_validation>' to 'int *'[/code]
You could store the index of the number instead of using a pointer.
[QUOTE=Overv;16119768]Awesome. Now, is there any shorter way to do the code between the equal signs?[/QUOTE]
How about
[cpp]
int* pfn = &*(numbers.begin() + 1);
[/cpp]
I have no idea if it will work.
Hmm, it seems only this works:
[cpp]std::list<int>::iterator it = numbers.begin( );
it++;[/cpp]
The following causes an error:
[cpp]std::list<int>::iterator it = numbers.begin( );
it += 1;[/cpp]
[code]error C2676: binary '+=' : 'std::list<_Ty>::_Iterator<_Secure_validation>' does not define this operator or a conversion to a type acceptable to the predefined operator[/code]
Looks like I'm gonna need a function.
[QUOTE=Overv;16121113]Hmm, it seems only this works:
[cpp]std::list<int>::iterator it = numbers.begin( );
it++;[/cpp]
The following causes an error:
[cpp]std::list<int>::iterator it = numbers.begin( );
it += 1;[/cpp]
[code]error C2676: binary '+=' : 'std::list<_Ty>::_Iterator<_Secure_validation>' does not define this operator or a conversion to a type acceptable to the predefined operator[/code]
Looks like I'm gonna need a function.[/QUOTE]
it += 1; doesn't work but it = it + 1; does.
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