please help me

cocos2d-x C++
#1

CCArray frames = CCArray::create;
for {
CCStringstr = CCString::createWithFormat(“a%04d.png”, i);

CCLog(str~~>getCString);
frames~~>addObject(CCSpriteFrameCache::sharedSpriteFrameCache()>spriteFrameByName));
}
CCAnimation animation = CCAnimation::create;
CCAnimatea = CCAnimate::create;
this>runAction(a);

Always crash here with：
Assertion failed!
Expression:dynami_cast<CCAnimationFrame*>(*arr)

how can i fix this?