How to properly use structs in c++? - c++

Question

I have a data structure in a header file of a player and a goblin that looks like this:
#ifndef GLOBALVAR_H
#define GLOBALVAR_H
#include <iostream>
#include <windows.h>
struct Player {
int x = 1, y = 1;
int health = 100;
int symbol = '#';
};
struct Goblin {
int x, y;
int health = 100;
int symbol = 'G';
};
#endif
I also have a data structure in a header file for the screen that looks like this:
#ifndef SCREEN_H
#define SCREEN_H
#include <iostream>
#include <windows.h>
struct Screen {
char screen[21][34] = {
"#################################",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#...............................#",
"#################################"
};
};
#endif
Finally, I have the main and generate c++ files that look like this respectively:
// main 'hub' for game
#include <iostream>
#include <windows.h>
#include "screen.h"
#include "generate.h"
#include "globalVar.h"
using namespace std;
bool running = true;
int main() {
struct Player p;
struct Screen s;
while(running) {
system("cls");
s.screen[p.y][p.x] = p.symbol;
draw();
p.health--;
system("pause>nul");
}
return 0;
}
// generates the map and draws the screen
#include <iostream>
#include <windows.h>
#include "screen.h"
#include "globalVar.h"
using namespace std;
int generate() {
return 0;
}
int draw() {
struct Screen s;
struct Player player;
for(int i = 0; i < 20; i++) {
cout << s.screen[i] << endl;
}
for(int i = 0; i < 1; i++) {
cout << "HP: " << player.health << endl;
}
return 0;
}
When I run main.cpp I want it to display a '#' symbol at 1, 1 of the array. When I run the code it instead displays a period in the place of it. What is happening here?
Image of what's being displayed:
https://imgur.com/a/RiWoDJ5

Answer 1

You have created two different Screens. The one in main() is completely different from the one in draw(), because they are in different scopes. You can pass a Screen as an argument to draw() to fix this.
You can also make draw() a function of Screen, as Nathan pointed out in the comments, and then call s.draw() in main().
Also, unlike in C, there is no need to put struct before every use of a struct. Simply put Screen s; instead of struct Screen s;
Example of draw() taking a parameter of type Screen:
int draw(Screen s) {
Player player;
for (int i = 0; i < 20; i++) {
cout << s.screen[i] << endl;
}
for (int i = 0; i < 1; i++) {
cout << "HP: " << player.health << endl;
}
return 0;
}
Example of draw() in Screen:
struct Screen {
static char screen[21][34];
int draw() {
Player player; //think about passing this as a parameter instead, not making one every time, because this one is inaccessible to everyone except this function
for (int i = 0; i < 20; i++) {
cout << screen[i] << endl;
}
for (int i = 0; i < 1; i++) {
cout << "HP: " << player.health << endl;
}
return 0;
}
};
Then, call it like:
s.draw();

Answer 2

I would go a different route and use inheritance and constructors:
struct Item
{
int m_x, m_y; // Every item has a position.
char m_symbol;
Item (char symbol, int x_pos = 1, int y_pos = 1)
: m_symbol(symbol), m_x(x_pos), m_y(y_pos)
{ ; }
};
struct Player : public Item // A player is an item
: Item('#', 1, 1)
{
};
struct Goblin : public Item // A goblin is an item
: Item ('G', 5, 4)
{
};
std::vector<std::vector<Item *>> game_board;
//...
Goblin * p_goblin = new Goblin;
game_board[p_goblin->y][p_goblin->x] = p_goblin;