Problem with class that inherit from Sprite

[paulocoutinhox]

Hi,

Im with a problem that i don't understand what is wrong.

I have a class Weapon that inherit from Sprite:

WEAPON

#pragma once

#include "axmol.h"

namespace game::weapon
{

USING_NS_AX;

class Weapon : public Sprite
{
public:
    virtual Weapon *createWeapon() = 0;
    virtual void initializeData();
};

} // namespace game::weapon

BOMB

#pragma once

#include "weapons/Weapon.h"

namespace game::weapon
{

class Bomb : public Weapon
{
public:
    virtual Weapon *createWeapon() override;
    virtual void initializeData() override;
};

} // namespace game::weapon

BOMB IMPL

Weapon *Bomb::createWeapon()
{
    Weapon *weapon = static_cast<Weapon *>(Weapon::create("weapons/bomb/body.png"));
    weapon->initializeData(); // <--- CRASH HERE
    return weapon;
}

void Bomb::initializeData()
{
    setName("shoot");
    setScale(1.0f);
}

WEAPON IMPL

#include "weapons/Weapon.h"

namespace game::weapon
{

void Weapon::initializeData()
{
    //
}

} // namespace game::weapon

But when i try create a bomb and call their method initializeData it crash:

It is not null and when i comment the line weapon->initializeData(); it works without crash.

What im doing wrong?

Thanks.

[aismann]

What about your WEAPON IMPL ?

[paulocoutinhox]

I update the thread with it, has nothing.

[rh101]

A Sprite is not a Weapon, yet your code is trying to force it to be.

Weapon *Bomb::createWeapon()
{
    Weapon *weapon = static_cast<Weapon *>(Weapon::create("weapons/bomb/body.png"));  <== incorrect logic
    weapon->initializeData(); // <--- CRASH HERE
    return weapon;
}

A Weapon is a Sprite, but a Sprite is not necessarily a Weapon. You can cast from Weapon to Sprite, and vice-versa, if and only if that object is an instance of Weapon. When downcasting, prefer dynamic_cast over static_cast. A dynamic cast would do the necessary checks to ensure that the object is in fact an instance of the type you are casting to, otherwise it will result in a nullptr, which you can check for. With a static_cast, you wouldn't get the nullptr (as you noticed with the crash in your code).

It looks like you forgot to implement the static method Weapon::create(). You can't use the Sprite::create(), since it's creating an object of type Sprite (the base class).

[rh101]

Also, having createWeapon as a virtual method makes little sense. It would mean you need to have an instance of that weapon in order to create another instance. Unless, perhaps, your use-case is weapon spawning more copies of itself?

The correct logic is to have static create() convenience methods defined for each derived type.

[aismann]

I have a class Weapon that inherit from Sprite:

Better:
Weapon using a Sprite object and isn't a Sprite itself