Cocos2d-x 3.0数据结构——cocos2d::Map

cocos2d::Map<K,V>是使用std::unordered_map作为底层结构的关联式容器。 而std::unordered_map是一个存储键值对的关联式容器，它可以通过它们的键快速检索对应的值。 使用unordered_map，键通常是唯一的，而值则与这个键对应。

模版参数

注意：使用现代的c++，本地存储对象比堆存储对象好。所以请不要用new操作来分配cocos2d::Map<K,V>的堆对象，请使用栈对象。
如果真心想动态分配堆cocos2d::Map<K,V>，请将原始指针用智能指针来覆盖。

警告：cocos2d::Map<K,V>并不是cocos2d::Object的子类，所以不要像使用其他cocos2d类一样来用retain/release和引用计数内存管理。

示例

警告：cocos2d::Map

//create Map<K,V> with default size and add a sprite into it
auto sp0 = Sprite::create();
sp0->setTag(0);
Map<std::string,Sprite*> map0;
std::string mapKey0 = "MAP_KEY_0";
map0.insert(mapKey0,sp0);
log("The size of map is %zd.",map0.size()); 
//create a Map<K,V> with capacity equals 5
Map<std::string,Sprite*> map1(map0);
std::string mapKey1 = "MAP_KEY_1";
if(!map1.empty()){
    auto spTemp = (Sprite*)map1.at(mapKey0);
    log("sprite tag = %d",spTemp->getTag());
    auto sp1 = Sprite::create();
    sp1->setTag(1);
    map1.insert(mapKey1,sp1);      
    //get all keys,stored in std::vector,that matches the object
    std::vector<std::string> mapKeyVec;
    mapKeyVec = map1.keys();
    for(auto key : mapKeyVec)
    {
        auto spTag = map1.at(key)->getTag();
        log("The Sprite tag = %d,MAP key = %s",spTag,key.c_str());
        log("Element with key %s is located in bucket %zd",key.c_str(),map1.bucket(key));
    }
    log("%zd buckets in the Map container",map1.bucketCount());
    log("%zd element in bucket 1",map1.bucketSize(1));  
    //get a random object if the map isn't empty,otherwise it returns nullptr
    log("The random object tag = %d",map1.getRandomObject()->getTag());  
    //find(const K& key) can be used to search the container for an element with 'key'
    //erase(const_iterator position) remove an element with an iterator
    log("Before remove sp0,size of map is %zd.",map1.size());
    map1.erase(map1.find(mapKey0));
    log("After remove sp0,map1.size());
}  
//create a Map<K,Sprite*> map2(5);
map2.reserve(10);  //set capacity of the map

运行结果：

cocos2d: The size of map is 1.
cocos2d: sprite tag = 0
cocos2d: The Sprite tag = 1,MAP key = MAP_KEY_1
cocos2d: Element with key MAP_KEY_1 is located in bucket 1
cocos2d: The Sprite tag = 0,MAP key = MAP_KEY_0
cocos2d: Element with key MAP_KEY_0 is located in bucket 0
cocos2d: 2 buckets in the Map container
cocos2d: 1 element in bucket 1
cocos2d: The random object tag = 0
cocos2d: Before remove sp0,size of map is 2.
cocos2d: After remove sp0,size of map is 1.

最佳用法

类似cocos2d::Vector，参见上一篇博文。