Cocos3.0数据结构Value Map Vector

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cocos2d::Value

http://cn.cocos2d-x.org/article/index?type=cocos2d-x&url=/doc/cocos-docs-master/manual/framework/native/v3/data-structure/value/zh.md

cocos2d::Value是许多基本类型(int,float,double,bool,unsigned char,char*和std::string)还有std::vector<Value>,std::unordered_map<std::string,Value>和std::unordered_map<int,Value>这些类的包装类型。

你可以将上面提及的基本类放进cocos2d::Value对象将它们转换成对应的类型，反之亦然。

注意：当处理基本类型和和容器时，请使用cocos2d::Vector<T>,cocos2d::Map<K,V>和cocos2d::Value。

cocos2d::Value的内存由它的析构函数来释放，所以使用cocos2d::Value时请尽量用推荐的最佳做法。

注意：cocos2d::Value不能像其它cocos2d类型一样使用retain/release和refcount内存管理

当要使用基本类型的聚合时，将基本类型包装成cocos2d::Value，然后将它们和模版容器cocos2d::Vector和cocos2d::Map联合使用。

实例:

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Value val;   // call the default constructor
if(val.isNull()) {
    log("val is null");
}else{
    std::string str =val.getDescription();
    log("The description of val0:%s",str.c_str());
}
//----------------------------------------------------
Value val1(65);   // initialize with a integer
//Value val1(3.4f);   // initialize with a float value
//Value val1(3.5);   // initialize with a double value
log("The description of the integer value:%s",val1.getDescription().c_str());
log("val1.asByte() = %c",val1.asByte());
//----------------------------------------------------
std::string strV = "string";
Value val2(strV);   // initialize with string
log("The description of the string value:%s",val2.getDescription().c_str());
//----------------------------------------------------
auto sp0 = Sprite::create();
Vector<Object*>* vecV = newVector<Object*>();
vecV->pushBack(sp0);
Value val3(vecV);   // initialize with Vector
log("The description of the Vector value:%s",val3.getDescription().c_str());
deletevecV;
//----------------------------------------------------
Map<std::string, Object*>* mapV = newMap<std::string, Object*>();
mapV->insert(strV,sp0);
Value val4(mapV);   // initialize with Map
log("The description of the Map value:%s",val4.getDescription().c_str());
deletemapV;
//----------------------------------------------------
Value val6(&val4);   // initialize with Map
log("The description of the Value-type value:%s",val6.getDescription().c_str());
//----------------------------------------------------
val2 = val1;   // assigning between 2 Value-type
log("operator-> The description of val2:%s",val2.getDescription().c_str());
val2 = 4;   //assigning directly
log("operator-> The description of val4:%s",val2.getDescription().c_str());

cocos2d::Vector

http://cn.cocos2d-x.org/article/index?type=cocos2d-x&url=/doc/cocos-docs-master/manual/framework/native/v3/data-structure/vector/zh.md

cocos2d::Vector<T>为cocos2d::CCArray的替代品

事件复杂度为：

随机访问，O(1)
将元素插入到尾部或者删除尾部的元素，O(1)
随机插入或删除, O(n)
内存管理：

cocos2d::Vector<T>类只包含一个成员数据：

std::vector<T> _data;

_data的内存管理是由编译器自动处理的

实例:

//create Vector<Sprite*> with default size and add a sprite into it
auto sp0 = Sprite::create();
sp0->setTag(0);
//here we use shared_ptr just as a demo. in your code, please use stack object instead
std::shared_ptr<Vector<Sprite*>>  vec0 = std::make_shared<Vector<Sprite*>>();  //default constructor
vec0->pushBack(sp0);
 
//create a Vector<Object*> with a capacity of 5 and add a sprite into it
auto sp1 = Sprite::create();
sp1->setTag(1);
 
//initialize a vector with a capacity
Vector<Sprite*>  vec1(5);
//insert a certain object at a certain index
vec1.insert(0, sp1);
 
//we can also add a whole vector
vec1.pushBack(*vec0);
 
for(auto sp : vec1)
{
    log("sprite tag = %d", sp->getTag());
}
 
Vector<Sprite*> vec2(*vec0);
if(vec0->equals(vec2)) { //returns true if the two vectors are equal
    log("pVec0 is equal to pVec2");
}
if(!vec1.empty()) {  //whether the Vector is empty
    //get the capacity and size of the Vector, noted that the capacity is not necessarily equal to the vector size.
    if(vec1.capacity() == vec1.size()) {
        log("pVec1->capacity()==pVec1->size()");
    }else{
        vec1.shrinkToFit();  //shrinks the vector so the memory footprint corresponds with the number of items
        log("pVec1->capacity()==%zd; pVec1->size()==%zd",vec1.capacity(),vec1.size());
    }
    //pVec1->swap(0, 1);  //swap two elements in Vector by their index
    vec1.swap(vec1.front(), vec1.back());  //swap two elements in Vector by their value
    if(vec2.contains(sp0)) {  //returns a Boolean value that indicates whether object is present in vector
        log("The index of sp0 in pVec2 is %zd",vec2.getIndex(sp0));
    }
    //remove the element from the Vector
    vec1.erase(vec1.find(sp0));
    //pVec1->erase(1);
    //pVec1->eraseObject(sp0,true);
    //pVec1->popBack();
 
    vec1.clear();//remove all elements
    log("The size of pVec1 is %zd",vec1.size());
}

cocos2d::Map

http://cn.cocos2d-x.org/article/index?type=cocos2d-x&url=/doc/cocos-docs-master/manual/framework/native/v3/data-structure/map/zh.md

cocos2d::Map<K,V>是使用std::unordered_map作为底层结构的关联式容器。

在unordered_map内部，元素是无序，它们是根据键的哈希值来存取的，存取的时间复杂度是常量，超级快。

在Cocos2d-x v3.0beta之前，使用的是另外一种顺序式容器cocos2d::CCDictionary,不过它将很快被废弃。

设计者们谨慎地设计了cocos2d::Map<K,V>用来替代cocos2d::CCDictionary，所以应该尽量使用cocos2d::Map而不是cocos2d::CCDictionary

模板参数:

cocos2d::Map<K,V>类只包含一个数据成员：

typedefstd::unordered_map<K, V> RefMap;

RefMap _data;

_data的内存管理是由编译器处理的，当在栈中声明cocos2d::Map<K,V>对象时，无需费心释放它占用的内存。但是如果你是使用new操作来动态分配cocos2d::Map<K,V>的内存的话，就得用delete来释放内存了，new[]操作也一样。

实例:

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//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, size of map is %zd.",map1.size());
} 
//create a Map<K, V> with capacity equals 5
Map<std::string, Sprite*> map2(5);
map2.reserve(10); //set capacity of the map

结果是：

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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 removesp0, size of map is 2.
cocos2d: After removesp0, size of map is 1.

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