I don't understand about drawing in SFML Game Development book

[aratnon]

It tells me to make a SceneNode class which inherits from sf::Drawable and sf::Transformable so I can draw by pass it as a paremter for the RenderWindow.draw() function

what I don't understand is for example, I have a SceneNode as a top of the SceneGraph then I call RenderWindow.draw(SceneNode). The result is every child node of SceneNode also draws too.
How it could be possible?

[eXpl0it3r]

Well turn to page 60 of the book, it's explained there.

It simply draws all the children in a loop.

[aratnon]

I have a epub version so, I dont know what is the page 60 actually in the book 
but I guess.

This is the draw function of The SceneNode class

void SceneNode::draw(sf::RenderTarget &target, sf::RenderStates states) const
{
        states.transform *= getTransform();
        drawCurrent(target, states);

        for each (const SceneNode::SceneNodePtr  &child in _children)
        {
                child->draw(target, states);
        }

}

In The World class I call this function to render the parent node

_renderWindow->draw(_sceneGraph);

after I call it. Does the _sceneGraph call

void SceneNode::draw(sf::RenderTarget &target, sf::RenderStates states)

by itself?

[Nexus]

Does the _sceneGraph call

void SceneNode::draw(sf::RenderTarget &target, sf::RenderStates states)

by itself?

Exactly, that's the recursive function call here:

child->draw(target, states);

By the way:

for each (const SceneNode::SceneNodePtr  &child in _children)

This syntax is a non-portable extension, not standard C++. You should use

for (const SceneNodePtr& child : children)

if your compiler supports range-based for, or our standard-conforming workaround

FOREACH(const SceneNodePtr& child, children)