c++ - 通过复制捕获 Lambda 函数会导致数据损坏

Question

std::vector<Spell*> playerSpells{ new Jump(1), new Arrow() };   

for (int i = 0; i < playerSpells.size(); i++)
{
    player->addSpell(playerSpells[i]);
}

for (int i = 0; i < player->getSpells().size(); i++)
{
    auto spell = player->getSpells()[i];

    player->getSpells()[i]->icon->onClickEndEH.add([=]() {
        auto a = player->getSpells()[i];
        auto b = player->getSpells()[i]->sprite;
    });
}

首先，我检查了spell 变量，它的字段已正确初始化。调用 lambda 函数时，变量 b 已损坏。如果这还不够，我可以提供代码的其他部分。

我尽量简化了；

//GAMEOBJECT.H
class GameObject
{
public:
    cocos2d::Sprite* sprite = nullptr;

    GameObject(const std::string fileName = "", bool clickable = false);
    ~GameObject();
};


//GAMEOBJECT.CPP
GameObject::GameObject(const std::string fileName, bool addClickEvent)
{
    if (fileName != "")
    {
        this->sprite = Sprite::create(fileName);
    }
    else
    {
        this->sprite = Sprite::create();
    }

    if (addClickEvent)
    {
        this->addTouchListener();
        this->clickable = true;
    }
}

GameObject::~GameObject()
{
    Director::getInstance()->getEventDispatcher()->removeEventListener(this->listener);
}

//SPELL.H
class Spell : public GameObject
{
public:
    GameObject* icon = nullptr;

    Spell(const std::string fileName = "", bool clickable = false);
    ~Spell();
}

//SPELL.CPP
Spell::Spell(const std::string fileName, bool clickable) : GameObject(fileName, clickable)
{
}

Spell::~Spell()
{
    delete icon;
}

//ARROW.H
class Arrow : public Spell
{
public:
    Arrow();
    ~Arrow();
};

//ARROW.CPP
Arrow::Arrow() : Spell("arrow.png")
{
    this->icon = new GameObject("arrow.png", true);
}

Answer 1

通过添加 retain() 和 release() 函数解决了这个问题。我认为 cocos2dx 检查它的池并删除 Sprite ，因为它没有被添加到范围内的场景中。

GameObject::GameObject(const std::string fileName, bool addClickEvent)
{
    if (fileName != "")
    {
        this->sprite = Sprite::create(fileName);
    }
    else
    {
        this->sprite = Sprite::create();
    }

    this->sprite->retain();

    if (addClickEvent)
    {
        this->addTouchListener();
        this->clickable = true;
    }
}

GameObject::~GameObject()
{
    this->sprite->release();
    Director::getInstance()->getEventDispatcher()->removeEventListener(this->listener);
}