How to concatenate name of variables in Cpp?

Question

I have class Walls in my program. Inside of class are objects Wall1, Wall2 etc. I want to do something like this: class definition:

class Walls {
    
public:
    Walls(){
        nPositionX = nMapWidth - 1;
        nHoleSize = 1;
        nHolePosition = rand()%(nMapHeight - nHoleSize);
        count++;
    }
    static int getCount() {
        return count;
    }
    int getPositionX()
    {
        return nPositionX;
    }
    
    
private:
    int nPositionX;
    int nHolePosition;
    int nHoleSize;
    static int count;
};

access to object

for (int i = 0; i < Walls::getCount(); i++) {
    
    int nPosx = Wall"i".getPositionX();
    
}
}

Is that possible in c++? Ok big thanks for everyone for help. I don't know why I didn't tried it before.

Or a std::map using name strings as keys, ie: std::map<std::string, Wall> walls; ... int nPosx = walls["Wall" + std::to_string(i)].getPositionX(); — Remy Lebeau
– Remy Lebeau, Commented Nov 17, 2020 at 17:00

Remy Lebeau · Accepted Answer · 2020-11-17 17:06:38Z

1

You can use an array or std::vector for that, eg:

std::array<Wall, MAX_WALLS> m_walls;
or
std::vector<Wall> m_walls;

...

// initialize m_walls[0], m_walls[1], etc as needed...

...

for (size_t i = 0; i < m_walls.size(); i++) {
    int nPosx = m_walls[i].getPositionX();
    ...
}

Or, you can use a std::map, eg:

std::map<std::string, Wall> m_walls;

...

// initialize m_walls["Wall1"], m_walls["Wall2"], etc as needed...

...

for (int i = 1; i <= getCount(); i++) {
    int nPosx = m_walls["Wall" + std::to_string(i)].getPositionX();
    ...
}

answered Nov 17, 2020 at 17:06

Remy Lebeau

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Comments

463035818_is_not_an_ai · Accepted Answer · 2020-11-17 17:06:20Z

1

The code is not executed until you execute your program, but in the executable there are no variable names anymore. Hence, no.

You can use an array or vector:

struct Wall { int get_position() const { return 42; } };
using Walls = std::vector<Wall>;

Walls walls;
for (const auto& wall : walls) {
    int nPosx = wall.get_position();
}

Or if you really want to map names to objects, use a std::map:

std::map<std::string,Wall> named_walls;

named_walls["stone wall"] = Wall();

answered Nov 17, 2020 at 17:06

463035818_is_not_an_ai

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