从迭代器调用函数(Calling functions from an iterator)

 我的Game类的drawScreen()函数出错了。 
 
void Game::drawScreen()
{
    window->clear();

    std::vector<sf::Drawable*>::iterator itr;

    for(int i = 0; i <= window->getSize().y; i++)
    {
        for(itr=drawableStack.begin(); itr!=drawableStack.end(); drawableStack.pop_back())
        {
            if(**itr.getPosition().y == i)
            {
                window->draw(**itr);
            }
        }
    }

    window->display();
}
 
 声明了可绘制堆栈 
 
std::vector<sf::Drawable*> drawableStack;
 
 错误发生在 
 
if(**itr.getPosition().y == i)
 
 它不喜欢**itr.getPosition() ，我不确定在它的位置使用什么。 此外，此功能的目标是从屏幕顶部向下绘制，以便首先绘制“更远”的东西，并在它们之上绘制更接近前景的对象。 如果这似乎不是一个有效的方法，让我知道什么会更好。 我担心当绘制一堆物体时，这可能会变慢。 

I'm getting an error in the drawScreen() function of my Game class.
 
void Game::drawScreen()
{
    window->clear();

    std::vector<sf::Drawable*>::iterator itr;

    for(int i = 0; i <= window->getSize().y; i++)
    {
        for(itr=drawableStack.begin(); itr!=drawableStack.end(); drawableStack.pop_back())
        {
            if(**itr.getPosition().y == i)
            {
                window->draw(**itr);
            }
        }
    }

    window->display();
}
 
The drawable stack is declared
 
std::vector<sf::Drawable*> drawableStack;
 
The error is at
 
if(**itr.getPosition().y == i)
 
It doesn't like the **itr.getPosition() and I'm not sure what to use in its place. Also, the goal of this function is to draw from the top of the screen down, so that things "farther away" are drawn first and objects closer to the foreground are drawn on top of them. If this doesn't seem like an efficient method of doing that let me know what would be better. I'm concerned that this may be slower when there's a bunch of objects being drawn.

原文：https://stackoverflow.com/questions/19144423