cocos2dx 3.x schedule error - c++

Question

When I try implement add one node per n seconds, the procedure crashes.
if I just run runBlock(0.0f), the procedure runs normally.
This is my code
MainLayer.cpp
bool MainLayer::init(){
if (!Layer::init()){
return false;
}
block_array = new std::vector<block*>();
Size visibleSize = Director::getInstance()->getVisibleSize();
auto body = PhysicsBody::createEdgeBox(visibleSize,PHYSICSBODY_MATERIAL_DEFAULT, 3.0);
body->setCategoryBitmask(0x0001);
body->setCollisionBitmask(0x0001);
body->setContactTestBitmask(0x0000);
body->getShape(0)->setRestitution(0.0);
auto edgeNode = Node::create();
edgeNode->setPosition(Vec2(visibleSize.width / 2, visibleSize.height / 2));
edgeNode->setPhysicsBody(body);
this->addChild(edgeNode);
auto sp = Sprite::create("CloseNormal.png");
sp->setTag(PLAYER);
auto sp_body = PhysicsBody::createCircle(sp->getContentSize().width / 2);
sp_body->setCategoryBitmask(0x003);
sp_body->setCollisionBitmask(0x003);
sp_body->setContactTestBitmask(0x001);
sp->setPhysicsBody(sp_body);
sp->setPosition(visibleSize / 2);
this->addChild(sp);
initBlock();
/**
When run function "runBlock", process crash!!
*/
schedule(schedule_selector(MainLayer::runBlock), 5.0f, CC_REPEAT_FOREVER, 0.0f);
//runBlock(0.0f); if just run it, everything is right
return true;
}
void MainLayer::initBlock(){
block_array->push_back(new block1()); //block is other class, it has no problem
block_array->push_back(new block2());
block_array->push_back(new block3());
}
void MainLayer::runBlock(float dt){
Size size = Director::getInstance()->getVisibleSize();
int len = block_array->size();
block* bl;
do
{
int rand = floor(CCRANDOM_0_1()*len);
if (rand == len){
rand -= 1;
}
bl = (*block_array)[rand];
} while (bl->node->getParent()); //Crash in here!!!!!
bl->come(Vec2(size.width*1.5, 0));
this->addChild(bl->node);
}
I use VS2013. The error info is
Without exception handling in 0x009D5402(in test.exe) 0xC0000005: Access violation when reading location 0xFEEF0012
I have debug. "bl->node" is allocated memory. So I don't think it is NULL pointer error. However, I don't know what reason cause the crash.
Please help me, Thanks!

Answer 1

After a few frames all your blocks will have parents and the while loop will never exit.
I don't really understand what it is you're trying to accomplish here, but might I suggest keeping two arrays, filling the first in initBlocks(), randomly picking one in runBlock(), processing it, and moving it to the second array.
This way you don't need the while loop, which wastes a lot of time if you keep picking a block that you've already processed.

Answer 2

Do it this way:
void MainLayer::runBlock(float dt)
{
Size size = Director::getInstance()->getVisibleSize();
//waiting_block_array = block_array when you initialize
if (waiting_block_array)
{
int rand = random (0, waiting_block_array.size () - 1);
addChild (waiting_block_array[rand]);
waiting_block_array[rand]->come(Vec2(size.width*1.5, 0));
this->addChild(waiting_block_array[rand]->node);
waiting_block_array.erase (waiting_block_array.begin () + rand);
}