CODEWITHSUNDEEP
c++
erbal
erbal

Reputation: 727

Why can't I declare a vector in a .h file?

I have a tiny .h file:

#include "stdafx.h"
#ifndef BIGNUM_H
#define BIGNUM_H
#include <vector>

class bignum{

private:
    std::vector<int> num;
    num.resize(4);

};
#endif

I get the following error messages:

What am I missing?

Upvotes: 3

Views: 2494

Answers (2)

juanchopanza
juanchopanza

Reputation: 227400

You cannot call num.resize(4); outside of a function. You could use your class' constructor, or a C++11 initialization at the point of declaration.

class bignum
{
private:
    std::vector<int> num = std::vector<int>(4); // C++11
};

class bignum
{
    bignum() : num(4) {} // C++03 and C++11
private:
    std::vector<int> num;
};

Upvotes: 4

Borgleader
Borgleader

Reputation: 15916

You can't call a method on a member variable inside your class declaration. If you want to resize the vector to 4 do so in the class constructor (or in another function but the constructor is by far the best place to do so).

In your cpp file you could do something like:

bignum::bignum() { num.resize(4); }

or:

bignum::bignum(): num(4) {}

The second one calls the vector constructor that takes a size argument. Or you can directly do it in your .h file:

class bignum{
    bignum(): num(4) {} // version 1
    bignum(): num() { num.resize(4); }  // version 2

private:
    std::vector<int> num;
};

Upvotes: 11

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