C++, SDL and Inheritance question.

[epicasian]

Okay, I'm stumped. I have a class named tnt_SpriteAnimation which derives from the class tnt_Sprite. In main, I create a new instance of tnt_SpriteAnimation (called test), which in the constructor, takes a file name argument, width and height. When I try to draw the sprite to the screen, I get nothing. However, if I change the instance "test" to a tnt_Sprite, I see the sprite sheet rendered to the screen. Why if the type is tnt_Sprite the sprite sheet is rendered and not rendered if the type is tnt_SpriteAnimation?

All help is greatly appreciated,
~EpicAsian

[GroundUpEngine]

Do you have virtual functions in your base class? because they could of been overwritten e.g.

Code: Select all

class tnt_Sprite {
  virtual void render() { // render, render, render };
}

class tnt_SpriteAnimation : public tnt_Sprite {
  void render() { // nothing };
}

[Ginto8]

Also, rather than naming everything tnt_*, you should look into namespaces for your library/engine.

[epicasian]

Do you have virtual functions in your base class? because they could of been overwritten e.g.

Code: Select all

class tnt_Sprite {
  virtual void render() { // render, render, render };
}

class tnt_SpriteAnimation : public tnt_Sprite {
  void render() { // nothing };
}

Thank you, GroundUpEngine, I knew I mus have missed something obvious (again). That usually happens when I'm tired .

Also, rather than naming everything tnt_*, you should look into namespaces for your library/engine.

I never really though of using namespaces, I'll look into it.

Thanks for all the help,
~EpicAsian

[GroundUpEngine]

No prob namespaces?

Code: Select all

namespace tnt
{
  class Sprite {
    // stuff
  };
}

main.cpp

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using namespace tnt;
Sprite playa; // Now I can use tnt::Sprite

[epicasian]

No prob namespaces?

Code: Select all

namespace tnt
{
  class Sprite {
    // stuff
  };
}

main.cpp

Code: Select all

using namespace tnt;
Sprite playa; // Now I can use tnt::Sprite

I know what namepaces are, I just never really thought about using them with the engine. :D

~EpicAsian

[Falco Girgis]

No prob namespaces?

Code: Select all

namespace tnt
{
  class Sprite {
    // stuff
  };
}

main.cpp

Code: Select all

using namespace tnt;
Sprite playa; // Now I can use tnt::Sprite

I know what namepaces are, I just never really thought about using them with the engine. :D

~EpicAsian

Well you should.

The entire reason C++ introduced namespaces was because every C library appended its own little prefix to all of their global function calls. OpenGL:

Code: Select all

glSOMESHIT();

SDL:

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SDL_SOMESHIT()

A namespace is a much prettier, cleaner way of grouping together symbols within a single project/library/api.