cocos2d-x 3.0 中新的Vector类

（本文转自：ht[去掉我]tp://dev.bunnyhero.or[去掉我]g/2014/01/cocos2d-x-30-beta-the-new-vector-class/）

cocos2d-x 3.0 beta was recently released. one of the big new additions is the introduction of new container classes.

up until now, the cocos2d-x’s container classes were modelled after objective-c’s container classes (NSArray, NSDictionary, etc). now they are modelled after the standard c++ library’s containers (std::vector<T>, std::map<T>).

this post will show you a simple example of converting code from using the oldCCArray class to the new Vector class.

consider this cocos2d-x v2.x code:

// HelloWorld.hclass HelloWorld : public cocos2d::CCLayer{    //  ...    cocos2d::CCArray *_bullets;};// HelloWorld.cppusing namespace cocos2d;bool HelloWorld::init(){    if (!this->CCLayer::init())        return false;    //  ...    //  bullets    this->_bullets = CCArray::createWithCapacity(100);    this->_bullets->retain();}

let’s review some things about the old CCArray class:

• they can only contain CCObject* (i.e. pointers to CCObject). you have to cast its elements to a subclass if you’re storing a bunch of CCSprite*s, for example.
• they are allocated on the heap using CCArray::create(), and follow cocos2d-x memory management rules (must be retain()ed andrelease()ed).

the new, 3.0 way might look like this:

// HelloWorld.hclass HelloWorld : public cocos2d::CCLayer{    //  other stuff...    cocos2d::Vector<cocos2d::Sprite *> _bullets;};// HelloWorld.cppusing namespace cocos2d;HelloWorld::HelloWorld() : _bullets(100){}

things to note here:

• cocos2d::Vector<T> is a template class. the type it contains must be a pointer to a subclass of cocos2d::Object (in this example, we are usingcocos2d::Sprite * — pointers to Sprites).
• _bullets, itself, is no longer a pointer. it’s a statically allocated object: nonew or create here. in general, the new container classes shouldn’t be allocated on the heap.
• we’re initializing _bullets in HelloWorld‘s constructor. if you wanted to initialize it in the init() method instead, you could use something like:this->_bullets = cocos2d::Vector<cocos2d::Sprite *>{100};. again, note that there is no new or create involved.

somewhere in some shooting code you might have something like this:

cocos2d-x v2.x:

//   add a bulletCCSprite *bullet = CCSprite::create("circle.png");this->_bullets->addObject(bullet);  //  retains bullet

cocos2d-x v3.0 beta:

//   add a bulletSprite *bullet = Sprite::create("circle.png")this->_bullets.pushBack(bullet);  //  retains bullet

not much different here except for the name change (pushBack is named similarly to the STL’s push_back method), and the fact that you use “.” instead of “->” (because _bullets is no longer a pointer).

removing an item:

v2.x:

this->_bullets->removeObject(bullet);

v3.0beta:

this->_bullets.eraseObject(bullet);

looping through the array:

v2.x:

//  loop through bulletsCCObject *obj;CCARRAY_FOREACH(this->_bullets, obj){    CCSprite *bullet = (CCSprite *)obj;    //  do something with bullet.    if (bullet->getPositionX() > 160)    {        //  ...    }}

v3.0beta:

//  loop through bulletsfor (auto bullet: this->_bullets){    //  do something with bullet.    //  no need to cast in this case    if (bullet->getPositionX() > 160)    {        //  ...    }}

and finally, in your destructor, you’d want to clean up the array so as not to leak memory:

v2.x:

HelloWorld::~HelloWorld(){    //  release stuff    this->_bullets->release();}

v3.0beta:

HelloWorld::~HelloWorld(){    //  nothing to do! _bullets manages its storage automatically when it falls out of scope}