First question is why are you’re using Vectors, nothing wrong with it just want to understand what you are trying to achieve.

So sprites appear and disappear, but eventually the number of sprites will get larger as levels progress, also making sprites unique by taging them. So thought Vector might be best solution to store sprites. Or should I use something else, should I not use vector, I am new so trying to understand best practise. 

the physics body is also stored with sprite..

Could you show us more code regarding declaring, initialising and adding them to the vector.

in .h
vector<Sprite*> _Sprites;

init() 
{

vector<Sprite*> _Sprites;

int random = rand() % 5;

auto sprite = Sprite::create("aSprite.png");
auto physicsBody = PhysicsBody::createBox(Size(65.0f , 81.0f ), PhysicsMaterial(0.1f, 1.0f, 0.0f));
sprite->setTag(random);
sprite->setPosition(cocos2d::Point((60 * random), (50 * random)));
physicsBody->setDynamic(false);
sprite->setPhysicsBody(physicsBody);

_Sprites.pushBack(sprite);
_Sprites.pushBack(sprite);
_Sprites.pushBack(sprite);

}

AnotherFunction
{
this->addchild(_Sprites.at(0));
this->addchild(_Sprites.at(1));
this->addchild(_Sprites.at(2));
}

This crashes in another function

{
this->addchild(_Sprites.at(0));
this->addchild(_Sprites.at(1));
this->addchild(_Sprites.at(2));
}

but this works fine if you only add one.

{
this->addchild(_Sprites.at(1));
}

init() 
{

vector<Sprite*> _Sprites;

int random = rand() % 5;
for (int i = 0; i < 3; i++)
{
auto sprite = Sprite::create("aSprite.png");
auto physicsBody = PhysicsBody::createBox(Size(65.0f , 81.0f ), PhysicsMaterial(0.1f, 1.0f, 0.0f));
sprite->setTag(random);
sprite->setPosition(cocos2d::Point((60 * random), (50 * random)));
physicsBody->setDynamic(false);
sprite->setPhysicsBody(physicsBody);

_Sprites.pushBack(sprite);
}

}

Use that code instead as you are only creating a single sprite and adding it. You can only add a sprite once to the scene.

But if its mulitple vectors each with a essentially ‘copy’ of the sprite wouldnt it be enough to differenciate it. The code above just loops it rather than manual pushback. So unsure of the difference it would make when adding it.

Your are pushing the same sprite, even though you have a vector of sprites they are the same single sprite, hence something like a loop is need.

Why would a loop make a difference as it looks esentially same thing? Or would I need to use a copy of those same sprites?

Wouldnt this differenciate it more if we put (i) on each element?

init() 
{

vector<Sprite*> _Sprites;

int random = rand() % 5;
for (int i = 0; i < 3; i++)
{
auto sprite(i) = Sprite::create("aSprite.png");
auto physicsBody(i) = PhysicsBody::createBox(Size(65.0f , 81.0f ), PhysicsMaterial(0.1f, 1.0f, 0.0f));
sprite(i)->setTag(random);
sprite(i)->setPosition(cocos2d::Point((60 * random), (50 * random)));
physicsBody(i)->setDynamic(false);
sprite(i)->setPhysicsBody(physicsBody(i));

_Sprites.pushBack(sprite(i));
}

}

In each loop iteration it creates a whole new sprite even though the name is the same.

The penny dropped :) many thanks for your help! Its working however some problems with random which I need to research.

Which is the best way of removing from layer then adding again? Do I have to use a method call sprite->retain()?

No retain required, use this->removeChild(nodeToBeRemoved); and add using this->addChild(nodeToBeAdded);

Also how do you know if a particular element is added to layer?

Honestly, don’t know.