[SOLVED] Static sf::Image and sf::Sprite?

[Pyrius]

I have a class which handles all of the drawing so far, so it has sf::Image's and sf::Sprite's. Those objects will always be the same, so I want to declare them static instead of loading the images and giving the sprites images in the constructor and accessing them with an object of that class. I want to do something like this:

Code: [Select]


class Foo
{
public:
      static void loadImages();

private:
      static sf::Image image;
      static sf::Sprite sprite;
};


Then in loadImages():

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void Foo::loadImages()
{
     Foo::image.LoadFromFile("image.png");
     Foo::sprite.SetImage(image);
}


But I can't compile it. I get the following errors:

"undefined reference to 'Foo::image'"
"undefined reference to 'Foo::sprite'"

I'm still learning about the static keyword, so I guess it's just a syntax error.

[Laurent]

I'm still learning about the static keyword

Google is often more helpful (and quick) than posting on a forum and waiting for an answer, especially for such a basic C++ problem
http://tinyurl.com/692z3ds

[Pyrius]

Hehe lmgtfy.com is awesome. I tried googling it but didn't get an answer. I didn't think about googling "undefined reference" for some reason...

[Nexus]

Don't you have a C++ book you learn with? If not, you should really buy or borrow a good one (like the C++ Primer), so that basics like the static keyword get explained in details. This is much more effective than when you have to google everything, and it leaves less knowledge gaps

[Pyrius]

Nope, I don't; I learned the basics through TheNewBoston (thenewboston.com), and I didn't learn static. Or, maybe I did, and I forgot about it.

EDIT: I give myself challenge programs to complete and when I need to know how to do something for that program that I don't know yet I look it up, and if I can't find an answer, I use the forum on cplusplus.com to ask for an answer.

[julen26]

You also should declare the static members outside the class.

Foo.cpp

Code: [Select]

sf::Image Foo::image;
sf::Sprite Foo::sprite;

[sbroadfoot90]

You also should declare the static members outside the class.

Foo.cpp

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sf::Image Foo::image;
sf::Sprite Foo::sprite;

No, they should be declared inside the class in the interface file Foo.h

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class Foo {
private:
   static sf::Image image;
   static sf::Sprite sprite;
}

and then defined (and initialised via default ctors) in the implementation file Foo.cpp

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sf::Image Foo::image;
sf::Sprite Foo::sprite;

Declaration is where the name and type of a something is made known to the compiler.

Definition (for objects) is where memory is set aside for the variable.

[Pyrius]

Yup, I found that out . Thanks for responding.