cocos2d正确创建和释放对象,引用计数器的使用

void Ref::release()
{
    CCASSERT(_referenceCount > 0, "reference count should greater than 0");
    --_referenceCount;
    
    if (_referenceCount == 0)
    {
#if defined(COCOS2D_DEBUG) && (COCOS2D_DEBUG > 0)
        auto poolManager = PoolManager::getInstance();
        if (!poolManager->getCurrentPool()->isClearing() && poolManager->isObjectInPools(this))
        {
            // Trigger an assert if the reference count is 0 but the Ref is still in autorelease pool.
            // This happens when 'autorelease/release' were not used in pairs with 'new/retain'.
            //
            // Wrong usage (1):
            //
            // auto obj = Node::create();   // Ref = 1, but it's an autorelease Ref which means it was in the autorelease pool.
            // obj->autorelease();   // Wrong: If you wish to invoke autorelease several times, you should retain `obj` first.
            //
            // Wrong usage (2):
            //
            // auto obj = Node::create();
            // obj->release();   // Wrong: obj is an autorelease Ref, it will be released when clearing current pool.
            //
            // Correct usage (1):
            //
            // auto obj = Node::create();
            //                     |-   new Node();     // `new` is the pair of the `autorelease` of next line
            //                     |-   autorelease();  // The pair of `new Node`.
            //
            // obj->retain();
            // obj->autorelease();  // This `autorelease` is the pair of `retain` of previous line.
            //
            // Correct usage (2):
            //
            // auto obj = Node::create();
            // obj->retain();
            // obj->release();   // This `release` is the pair of `retain` of previous line.
            CCASSERT(false, "The reference shouldn't be 0 because it is still in autorelease pool.");
        }
#endif
        delete this;
    }
}

上面是cocos2d 3.0 ref的release方法。

分析代码，这个函数主要做了什么：

1. 调用release方法，引用计数器 -1。

2.当引用计数器为0时，delete this 销毁对象。

重点看那段注释，告诉我们如何正确使用retain(),release(),new(), autorelease(),create():

注释代码举了两种错误的使用和两种正确使用的例子，总结起来就是：

1. retain(),release()配对使用。

2. new(), autorelease()配对使用。

3. new()对象后引用+1，是为autorelease()用的。