C++ and SDL Trouble Creating a STL Vector of a Game Object

Question

I am trying to create a Space Invaders clone using C++ and SDL. The problem I am having is in trying to create Waves of Enemies. I am trying to model this by making my Waves a vector of 8 Enemy objects.

My Enemy constructor takes two arguments, an x and y offset. My Wave constructor also takes two arguments, an x and y offset. What I am trying to do is have my Wave constructor initialize a vector of Enemies, and have each enemy given a different x offset so that they are spaced out appropriately.

Enemy::Enemy(int x, int y)
{
    box.x = x;
    box.y = y;
    box.w = ENEMY_WIDTH;
    box.h = ENEMY_HEIGHT;

    xVel = ENEMY_WIDTH / 2;
}

Wave::Wave(int x, int y)
{
    box.x = x;
    box.y = y;
    box.w = WAVE_WIDTH;
    box.y = WAVE_HEIGHT;

    xVel = (-1)*ENEMY_WIDTH;
    yVel = 0;

    std::vector<Enemy> enemyWave;
    for (int i = 0; i < enemyWave.size(); i++)
    {
        Enemy temp(box.x + ((ENEMY_WIDTH + 16) * i), box.y);
        enemyWave.push_back(temp);
    }
}

I guess what I am asking is if there is a cleaner, more elegant way to do this sort of initialization with vectors, or if this is right at all. Any help is greatly appreciated.

Answer 1

There are a couple of problems here.

Firstly, enemyWave is a local variable and gets destroyed at the end of the constructor when it goes out of scope, which makes it useless as a long term data structure.

Secondly, everything you store in a vector needs to follow the rule of three. It's not clear if your Enemy classes do.

Apart from that, this is pretty much how you initialise a vector, an element at a time.