Split function's declaration and definition, or delete new operator in header?

Question

I'm new in C++, and I have difficulty in my project.

Super.h

#pragma once
#include <iostream>

float *list=new float[10];

class Super{
public:
    void function(){}
};

A.h

#pragma once
#include "Super.h"

class A{  
public:
    void function();
};

A.cpp

#include "A.h"
void A::function(){
    std::cout<<"Working A!"<<std::endl;
}

main.cpp

#include "A.h"

int main(int argc, const char * argv[]) {
    A a;
    a.function();
    return 0;
}

This code is not compiled,(clang: error: linker command failed with exit code 1 (use -v to see invocation)) and I found if I delete

float *list=new float[10];

in Super.h, It compiled.

However, I need the array that can be accessed in class A. So I have tried many ways, and found it can be compiled if I leave float array, and combine A.h and A.cpp, like

//Super.h    

float *list=new float[10];

class Super{

public:
    void function(){}
};

------------------------------------
// A.h

#pragma once
#include "Super.h"


class A{

public:    
    void function();
};

void A::function(){
    std::cout<<"Working A!"<<std::endl;
}

Do I have to combine A.cpp and A.h? or is my design bad? I use XCode 8.

Answer 1

In your actual code, "line" is declared in Settings.h and used in it's drawPixel function.

The only other place that it's used is in main.cpp I'm going to discuss these points in reverse order so our discussion can make more sense:

• Cleanup: delete[] pixels You should be using a vector<float> instead so you avoid all the problems associated with dynamic memory:
  1. What if drawPixel is called after cleanup?
  2. What if your code exits with an error?
  3. How will you ensure that your main function doesn't exit early and miss this?
• Usage: glDrawPixels(width, height, GL_RGB, GL_FLOAT, pixels) The final glDrawPixels parameter is of type void* So, if you've correctly replaced pixels with a vector<float> you can make the implicit conversion by passing data(pixels)
• Initialization: fill_n(pixels, width*height * 3, 1.0f) Rather than in Settings.h, this is where pixels should be defined: vector<float> pixels(width * height * 3, 1.0F) you'll need to make these changes to your system to avoid the global variable:
  1. All instances of void draw() will need to be changed to void draw(vector<float>& pixels) and when any draw method is called pixels will be the argument
  2. void drawPixel(const int& i, const int& j, const float& red, const float& green, const float& blue) should be changed to void drawPixel(vector<float>& pixels, const int i, const int j, const float red, const float green, const float blue) and any call to the drawPixel function must take pixel as it's 1^st argument
  3. void drawLine(const int& i0, const int& j0, const int& i1, const int& j1, const float& red, const float& green, const float& blue) should be changed to void drawLine(vector<float>& pixels, const int i0, const int j0, const int i1, const int j1, const float red, const float green, const float blue) and any call to the drawLine function must take pixel as it's 1^st argument