Messages

1

General / Question regarding the creation of objects.

« on: August 03, 2015, 03:16:05 pm »

Hello everyone,

Why do you use:

sf::Sprite sprite

and not

sf::Sprite* sprite

What's the different and why should you use one over the other?
I know the first variable is created on the stack and the second one is a pointer to an object on the heap?
Isn't the stack limited so won't it be a problem once you start using lots of variables?

2

General / Re: SFML game dev book. Stuck at implementing the fire mechanic

« on: July 25, 2015, 12:49:36 pm »

What happens if you change the lambda to pass variables (here fn) by reference (changing [=] to [&])?

But besides that, anything stopping you from just defining another functor similar to the others?

Changing the lambda to pass by reference breaks it. It compiles and launches after a couple of actions it gives an error.

Nothing is stopping me from creating functors at the moment.
Thanks

3

General / Re: SFML game dev book. Stuck at implementing the fire mechanic

« on: July 25, 2015, 09:16:31 am »

So fixing your code might be as simple as moving the object creation into its own line and essentially caching the passed object for a bit:

Code: [Select]

{
    auto &shotbinding = std::bind(&Aircraft::fire, std::placeholders::_1);
    m_ActionBinding[Fire].action = derivedAction<Aircraft>(shotbinding);
}

I tried moving it right now to a different line seems like the actual binding it doesn't give a problem. Passing it to the template gives the problem. It's not fixed with changing it to a seperate line.

This is the code for the template

template <typename GameObject, typename Function>
Command::Action derivedAction(Function fn)
{
    return[=](SceneNode& node, sf::Time dt)
    {
        //Check if cast is safe
        assert(dynamic_cast<GameObject*>(&node) != nullptr);

        //Downcast node and invoke function on it;
        fn(static_cast<GameObject&>(node), dt);
    };
}

edit:
What I did for now was make a struct like this

struct FireMech
{
    FireMech()
    {

    }
    void operator() (Aircraft& aircraft, sf::Time dt) const
    {
        aircraft.fire();
    }
};

This works and the fire method executes and I can link it. Although I'm still hoping there is a solution for the std::bind problem.

4

General / SFML game dev book. Stuck at implementing the fire mechanic

« on: July 24, 2015, 11:38:13 am »

Hello everyone,

I'm currently working through the SFML game dev book but I stumbled upon a problem that I can't seem to fix.
This is the method that handles initializing the actions.

void Player::initializeActions()
{
    m_ActionBinding[MoveRight].action = derivedAction<Aircraft>(AircraftMover(1, 0.f));
    m_ActionBinding[MoveLeft].action = derivedAction<Aircraft>(AircraftMover(-1, 0.f));
    m_ActionBinding[MoveUp].action = derivedAction<Aircraft>(AircraftMover(0.f, -1));
    m_ActionBinding[MoveDown].action = derivedAction<Aircraft>(AircraftMover(0.f, 1));
    m_ActionBinding[Fire].action = derivedAction<Aircraft>(std::bind(&Aircraft::fire, std::placeholders::_1));
}
 

When I compile I get this error:

Error   1       error C3848: expression having type 'const std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall Aircraft::* )(void),void,Aircraft,>,std::_Ph<1> &>' would lose some const-volatile qualifiers in order to call 'void std::_Bind<true,void,std::_Pmf_wrap<void (__thiscall Aircraft::* )(void),void,Aircraft,>,std::_Ph<1> &>::operator ()<GameObject&,sf::Time&>(GameObject &,sf::Time &)'      e:\_gamedevelopment\sfml\sfml_flyinggame\command.h      24
 

this is the method I'm trying to bind:

void Aircraft::fire()
{
    if (Table[m_Type].fireInterval != sf::Time::Zero)
    {
        m_IsFiring = true;
    }
}

I'm using Visual studio 2013 ( and it's compiler).

Thanks in advance.