Question

This is weird. I created a vector just fine in one class but can’t create it in another class. He’s a representation of what I have:

main.h

#include <Windows.h>
#include <ShellAPI.h>
#include <vector>
#include <string>
#include <iostream>

#include "taco.h"

class MyClass
{

public:
    int someint;
    vector<int> myOrder;
};

taco.h

#include <vector>

class OtherClass
{

public:
    vector<int> otherOrder;
};

And I get compile errors regarding the vector declaration in taco.h:

error C2143: syntax error : missing ';' before '<'
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
error C2238: unexpected token(s) preceding ';'

What am I missing here? I can uncomment out that second vector declaration and it compiles fine.

Answer 1

Try:

std::vector<int> otherOrder;

vector is part of the std namespace. This means that whenever you use a vector in a header file, you should include the std:: prefix.

The reason that you can sometimes get away with forgetting it is that some included files may have using namespace std; in them, allowing you to leave off the prefix. However, you should avoid the using keyword in header files, for it will pollute the namespace of any files that include it.

For a more detailed explanation of the dangers of using namespace ..., see this thread.