3.X：ActionManager动作管理类浅析：

1、Action类继承关系图，虽然这张图是2.X的版本，以为没找到3.X的这种图，

但是整体来说是一样的，CCFiniteTimeAction又分为CCActionInstanse（瞬时动作的基类）和CCActionInterval（延时动作的基类）

2、动作管理类分析：动作管理类，我们一般不需要直接使用，如果要是使用摸个动作，直接使用Node中的方法即可。3、整个动作的管理，跟下面这个结构密不可分//// singleton stuff//typedef struct _hashElement{    struct _ccArray     *actions; //一个Node上，可能又很多个action    Node                *target; //Node    int                 actionIndex;     Action              *currentAction; //当前的Action    bool                currentActionSalvaged; //是否被标记    bool                paused; //是否暂停    UT_hash_handle      hh; //hashTable} tHashElement;4、// main loop//这个update方法在每次循环的时候都会被调用，所有动作的执行处理，都是在这个函数中。void ActionManager::update(float dt){    for (tHashElement *elt = _targets; elt != nullptr; )    {        _currentTarget = elt;        _currentTargetSalvaged = false;        if (! _currentTarget->paused)        {// The 'actions' MutableArray may change while inside this loop.//这里循环Node的所有Action，因为一个Node可能又很多个Action            for (_currentTarget->actionIndex = 0; _currentTarget->actionIndex < _currentTarget->actions->num;                _currentTarget->actionIndex++)            {                _currentTarget->currentAction = (Action*)_currentTarget->actions->arr[_currentTarget->actionIndex];                if (_currentTarget->currentAction == nullptr)                {                    continue;                }                _currentTarget->currentActionSalvaged = false;//执行Action的step方法，这个方法会被继承自Action的具体动作类重写，如：(1)ActionInterval是有一段持续时间的动作void ActionInterval::step(float dt){    if (_firstTick)    {        _firstTick = false;        _elapsed = 0;    }    else    {        _elapsed += dt;    }    //这里调用update方法，更新动作，如MoveTo，需要更新坐标，位置等等    this->update(MAX (0,                                  // needed for rewind. elapsed could be negative                      MIN(1, _elapsed /                          MAX(_duration, FLT_EPSILON)   // division by 0                          )                      )                 );}(2) ActionInstant是立即执行的动作，这里就直接调用updatevoid ActionInstant::step(float dt) {    CC_UNUSED_PARAM(dt);    update(1);}                _currentTarget->currentAction->step(dt);                if (_currentTarget->currentActionSalvaged)                {                    // The currentAction told the node to remove it. To prevent the action from                    // accidentally deallocating itself before finishing its step, we retained                    // it. Now that step is done, it's safe to release it.                    _currentTarget->currentAction->release();                } else//判断是否结束，如果结束，就stop，并且从Node的Action数组中移除。                if (_currentTarget->currentAction->isDone())                {                    _currentTarget->currentAction->stop();                    Action *action = _currentTarget->currentAction;                    // Make currentAction nil to prevent removeAction from salvaging it.                    _currentTarget->currentAction = nullptr;                    removeAction(action);                }                _currentTarget->currentAction = nullptr;            }        }        // elt, at this moment, is still valid        // so it is safe to ask this here (issue #490)        elt = (tHashElement*)(elt->hh.next);        // only delete currentTarget if no actions were scheduled during the cycle (issue #481)        if (_currentTargetSalvaged && _currentTarget->actions->num == 0)        {            deleteHashElement(_currentTarget);        }    }    // issue #635    _currentTarget = nullptr;}