[英]How to access an interface-implementing object stored as pointer in an std::vector
So I have this: 所以我有这个:
std::vector<EnemyInterface*> _activeEnemies;
where EnemyInterface looks like this: EnemyInterface如下所示:
#include "Ogre.h"
class EnemyInterface{
public:
virtual void update(const Ogre::Real deltaTime) = 0;
virtual void takeDamage(const int amountOfDamage, const int typeOfDamage) = 0;
virtual Ogre::Sphere getWorldBoundingSphere() const = 0;
virtual ~EnemyInterface(){}
};
I create a new enemy: 我创建了一个新敌人:
// Spikey implements EnemyInterface
activeEnemies.push_back( (EnemyInterface*) &Spikey(_sceneManager, Ogre::Vector3(8,0,0)) );
And I want to call the update function on every enemy, but it crashes: 我想对每个敌人调用update函数,但是它崩溃了:
// update enemies
for (std::vector<EnemyInterface*>::iterator it=_activeEnemies.begin(); it!=_activeEnemies.end(); ++it){
(**it).update(timeSinceLastFrame); // Option 1: access violation reading location 0xcccccccc
(*it)->update(timeSinceLastFrame); // Option 2: access violation reading location0xcccccccc
}
I can see the enemy on screen, but I cannot access it. 我可以在屏幕上看到敌人,但无法访问它。 Any help would be appreciated.
任何帮助,将不胜感激。
Spikey.h looks like this: Spikey.h看起来像这样:
#include "EnemyInterface.h"
class Spikey: virtual public EnemyInterface{
private:
int thisID;
static int ID;
Ogre::SceneNode* _node;
Ogre::Entity* _entity;
public:
Spikey(Ogre::SceneManager* sceneManager, const Ogre::Vector3 spawnPos);
// interface implementation
virtual void update(const Ogre::Real deltaTime);
virtual void takeDamage(const int amountOfDamage, const int typeOfDamage);
virtual Ogre::Sphere getWorldBoundingSphere() const;
};
It's because you create a temporary object in your push_back
call. 这是因为您在
push_back
调用中创建了一个临时对象。 As soon as the push_back
function returns that object is no more, and leaves you with a dangling pointer. 当
push_back
函数返回该对象时,该对象就不再存在,并留下一个悬空的指针。
You have to create a new object using new
instead: 您必须使用
new
来创建一个新对象:
activeEnemies.push_back(new Spikey(_sceneManager, Ogre::Vector3(8,0,0)));
change 更改
activeEnemies.push_back( (EnemyInterface*) &Spikey(_sceneManager, Ogre::Vector3(8,0,0)) );
to 至
activeEnemies.push_back( new Spikey(_sceneManager, Ogre::Vector3(8,0,0)) );
And this is the correct call 这是正确的电话
(*it)->update(timeSinceLastFrame);
Your vector
contains EnemyInterface*
. 您的
vector
包含EnemyInterface*
。
So *it
gives you EnemyInterface*
- ie a pointer to EnemyInterface. 因此,
*it
为您提供了EnemyInterface*
-即指向EnemyInterface的指针。 You can call a method using pointer to an object by using ->
您可以使用
->
使用指向对象的指针来调用方法
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