accessing classes from a .h file in C++

Question

Hello I am new to using header files and OPP in my programs and I am wondering why visual studio 2010 is stating that there are errors in my code. The code compiles and runs as desired but there are red lines under all of the objects

here is the header file

//functions.h
#include "stdafx.h"
#include <iostream>
#include <ctime>
#include <string>

using namespace std;

class vehicle
{
public:
int hp;
int ammo;
void displayHP();
void displayAmmo();
void displayName();
string vesselName;
void setName(string);
void moveUP(int& y);
void moveDown(int& y);
void moveLeft(int &x);
void moveRight(int &x);
private:
};
 //implementation section
void vehicle::displayHP(){cout<<hp<<endl;}
void vehicle::displayAmmo(){cout<<ammo<<endl;}
void vehicle::setName(string name){vesselName=name;}
void vehicle::displayName(){cout<<vesselName<<endl;}
void vehicle::moveUP(int& y)
    {
        y=y-1;//moves boat up
        system("cls");  
    }
void vehicle::moveDown(int& y)
{
        y=y+1;//moves boat down
        system("cls");
}
void vehicle::moveLeft(int &x)
{
        x=x-1;// moves the boat left
        system("cls");      
}


void vehicle::moveRight(int &x)
{
    x=x+1;//moves boat right
    system("cls");
}
void moveBoat(int &x,int& y, int a,int b,int s,int turn)
{

here is the header file that contains the boats movements. The program compiles fine and works as designed but I was confused why visual studio is claiming there are so many errors I added line comments to where the errors in the boat.h file

//boat.h
#include "stdafx.h"
#include <iostream>
#include <ctime>
#include <string>
#include "functions.h"

using namespace std;

void moveBoat(int &x,int& y, int,int,int,int);
void youScrewedUp(int &x,int& y, int,int,int,int);



int movement=0;

 vehicle destroyer;
    destroyer.hp=500;//<==== getting a red line under the word destroyer error   says "this deceleration has no storage class or type specifier"
    destroyer.ammo=500;//<==== getting a red line under the word destroyer error   says "this deceleration has no storage class or type specifier"



displayArray(x,y,a,b,s);//<===="this deceleration has no storage class or type specifer"
destroyer.setName("USS YAY I LEARNED CLASSES");//<===="this deceleration has no storage class or type specifer"
destroyer.displayName();//<===="this deceleration has no storage class or type specifer"
destroyer.displayHP();//<===="this deceleration has no storage class or type specifer"
cout<<"Boat Location X "<<x<<" Y "<<y<<endl;
if(s==1)
{
cout<<"ENEMY SHIP SIGHTED"<<endl;//<===="this deceleration has no storage class or type specifer"
}
cout<<"1.move left"<<endl;//<===="this deceleration has no storage class or type specifer"
cout<<"2.move right"<<endl;//<===="this deceleration has no storage class or type specifer"
cout<<"3.move up"<<endl;//<===="this deceleration has no storage class or type specifer"
cout<<"4.move down"<<endl;//<===="this deceleration has no storage class or type specifer"
cin>>movement;<===="this deceleration has no storage class or type specifer"

    switch(movement)//<==expected a deceleration 
    {
    case 1:
        if(x>0)//does not allow boat to leave grid
        {
            destroyer.moveLeft(x);
        }
        else
        {
            youScrewedUp(x,y,turn,a,b,s);// function that repeats the movement function and displays a message
        }
        break;

        case 2:
        if(x<9)//boundary
        {
            destroyer.moveRight(x);
        }
        else
            {
            youScrewedUp(x,y,turn,a,b,s);
            }
        break;

        case 3:
        if(y>0)//boundary
        {
            destroyer.moveUP(y);
        }
        else
            {
            youScrewedUp(x,y,turn,a,b,s);
            }
        break;

        case 4:
        if(y<9)//boundary
        {
            destroyer.moveDown(y);
        }
        else
            {
            youScrewedUp(x,y,turn,a,b,s);
            }
        break;


    }
    turn++;//adds one to the turn counter to cycle to the enemies turn



}

void youScrewedUp(int &x, int &y,int turn, int a, int b,int s)// must pass the x y values by refferance
{
cout<<"where are you going your leaving the battlefield"<<endl;
            cout<<"please make another selection"<<endl;
            system("pause");
            system("cls");
            moveBoat(x,y,turn,a,b,s);
}

Here is my main()

// arrayTest.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "array.h"
#include "boat.h"
#include "enemy.h"
#include <iostream>
#include <ctime>

using namespace std;

int main()
{
int turn=1;// turn counter cycles between 1 and 2 during player and enemy turns
int x=7;//x coordinate for destroyer
int y=6;//y coordinate for destroyer            
int a=3;//x coordinate for sub
int b=4;//y coordinate for sub
int s=0;//toggle for submerged or not chose not to use a bool because I used a random number generator to allow a 25% chance opposed to a 50% chance
srand (time(NULL));

do{
    moveBoat(x,y,turn,a,b,s);//function that moves the boat
    moveEnemy(a,b,turn,x,y,s);//function to move the enemy
}while(turn<3);// this is temporary will be replaced when a hp and weapons system is completed
    system("pause");
return 0;
}

Answer 1

This goes beyond your base question and adds some other things that will improve your code and hopefully understanding.

1. You need to put your 'main' function code literally in a main function

   int main(int argc, char * argv[])
   {
       //do stuff here....
       return 0;
   }
   

2. You should include header guards to prevent you from including 'function.h' multiple times. I would also strongly suggest renaming it to Vehicle.h to be emblematic of the class it is providing.

   #ifndef __VEHICLE_H__
   #define __VEHICLE_H__
   //... all the good stuff.
   
   #endif
   

3. I would STRONGLY suggest you remove using namespace std from your header file as doing so will trash the namespaces of anyone who wishes to use your header. Instead simply use std:: where needed or if you really don't want to use them everywhere, consider doing a using std::xyz; for the specific features you are using. This way at least you can trace down collisions later. If you want to do this in an implementation file (i.e. *.c) that's up to you; but don't do it in files that are included generally speaking.

4. Don't include headers you aren't using in your header file. This is a bad habit, leads to code and compiler bloat, and will inevitably cause pain later. You shouldn't be including ctime or stdafx in each of your headers as they don't refer to it.

5. You need to put the body of 'stuff' that is floating inside boat.h into a function

   //somefunct
   void somefunction()
   {
       int movement=0;
   
       vehicle destroyer;
       destroyer.hp=500;//<==== getting a red line under the word destroyer error   says "this deceleration has no storage class or type specifier"
       destroyer.ammo=500;//<==== getting a red line under the word destroyer error   says "this deceleration has no storage class or type specifier"
   
   
       //.... Everything else
   
   }