CODEWITHSUNDEEP
c++
user1334858
user1334858

Reputation: 1945

Passing std::vector to function

I want to add some values to a vector in my c++ code but every time I try and send the vector to the function in my main.cpp file it underlines it in red and say:

 A nonstatic member reference mus be relative to a specific object.

In my Header:

#ifndef HEADER_H
#define HEADER_H
#include <vector>

namespace Functions{
    class MyClass
    {
    public:
        void fun(std::vector<char*> vect);

    };

}
#endif

.cpp file:

void Functions::MyClass::fun(std::vector<char*> vect){
    vect.push_back("value 1");
    vect.push_back("Save File Name");
}

Main.cpp

#include "Header.h"    
#include <vector>
int main(){ 
  std::vector<char*>vect;
  Functions::MyClass::fun(vect);
  return 0;
}

Upvotes: 0

Views: 2780

Answers (2)

Andy Prowl
Andy Prowl

Reputation: 126552

You are calling your fun() member function as if it were a static function. Since it is a regular member function instead, you should create an object on which to invoke it:

Functions::MyClass m;
m.fun(vect);

If your function does not need to work on any concrete instance of the class it is a member of, you can declare it as static. That would allow you to call it the way you are currently calling it.

Besides, as others have pointed out already, it is probably a good idea to pass the vector by reference:

void fun(std::vector<char*>& vect)
//                         ^

Passing by value will create a copy of the argument in vect, meaning that the calling function will not see any side-effect after the call to fun().

Also, a good idea is to use std::string rather than pointers to char (especially if not const):

#include <string> // Requires for std::string

// ...

void Functions::MyClass::fun(std::vector<std::string>& vect)
//                                       ^^^^^^^^^^^
{
    vect.push_back("value 1");
    vect.push_back("Save File Name");
}

Upvotes: 10

Ivaylo Strandjev
Ivaylo Strandjev

Reputation: 71009

You have two problems:

  1. You are calling a non-static function without an object. To fix that declare an object of type MyClass and call fun on it:

    int main(){ 
  Functions::MyClass a;
  std::vector<char*>vect;
  a.fun(vect);
  return 0;
}

  2. You only modify a local copy of vect in your function. To fix that pass the vector by reference to the function:

    void Functions::MyClass::fun(std::vector<char*>& vect){
  vect.push_back("value 1");
  vect.push_back("Save File Name");
}

Of course declaration should also be changed accordingly.

Upvotes: 4

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