I need to do custom deleter for shared_ptr. I know that this can be done in a similar way:
std::shared_ptr<SDL_Surface>(Surf_return_f(), MyDeleter);
But I would like to make them in the style of my custom deleter for unique_ptr:
struct SDL_Surface_Deleter {
void operator()(SDL_Surface* surface) {
SDL_FreeSurface(surface);
}
};
using SDL_Surface_ptr = std::unique_ptr<SDL_Surface, SDL_Surface_Deleter>;
Is there any way to do this?
It seems that you're trying to define a type alias that means "std::shared_ptr with my deleter type". There's no such thing, because std::shared_ptr has a type-erased deleter (the deleter is not part of the type).
Instead, you could create a custom version of make_shared:
template <class... Args>
std::shared_ptr<SDL_Surface> make_sdl_surface(Args&&... args) {
return std::shared_ptr<SDL_Surface>(new SDL_Surface(std::forward<Args>(args)...),
SDL_Surface_Deleter{});
}
Unlike a unique_ptr, the deleter for a shared_ptr is not part of the type. You must pass the deleter to the constructor of the shared_ptr.
You could wrap it in a function instead:
std::shared_ptr<SDL_Surface> make_shared_surface(SDL_Surface* surface)
{
return std::shared_ptr<SDL_Surface>(surface, MyDeleter);
}
and then call make_shared_surface(Surf_return_f()).
// use lambda expression for deleter for shared pointer
// I used this very code in my SDL wrapper classes except I use textures not surfaces
// note SDL_Surface* raw_surface_ptr is what you get from calling the SDL function
m_surface_ptr = std::shared_ptr< SDL_Surface >(
raw_surface_ptr,
[](SDL_Surface* s)
{
if (t) SDL_DestroySurface( t );
} );
