cocos2d::Value

• Since: v3.0 beta
• Language: C++

Defined in the head "CCValue.h" loated in "COCOS2DX_ROOT/cocos/base"

 
 

  
  
 
   
 
    
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class Value;
 
   
 
  
 
 

cocos2d::Value is a wrapper class for many primitives(int,float,double,bool,unsigned char,char* and std::string) plus std::vector<Value>,std::unordered_map<std::string,Value> and std::unordered_map<int,Value>.

You can put all the primitives mentioned above into a cocos2d::Value object and convert it to the corresponding primitive. The opposite is vice verse.

Internally,cocos2d::Value uses a union variable to hold all kinds of primitives which saves a lot of memory space.

Before cocos2d-x v3.0 beta,there are CCBool,CCFloat,CCDouble,CCinteger primitive wrapper. These classes will be deprecated in the future.

Note:When you deal with primitives and container,please use cocos2d::Vector<T>,cocos2d::Map<K,V> and cocos2d::Value.

Memory Management

The memory of cocos2d::Value is handled automatically by it's own destructor. So please stick to the best practice of c++ memory management rules when handling the memory of cocos2d::Value.

The cocos2d::Value class contains the following data members:

 
 

  
  
 
   
 
    
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union
{
    unsigned char byteVal;
    int intVal;
    float floatVal;
    double doubleVal;
    bool boolVal;
}_baseData;

std::string _strData;
ValueVector* _vectorData;
ValueMap* _mapData;
ValueMapIntKey* _intKeyMapData;

Type _type;
 
   
 
  
 
 

From the code snippets,_baseData,_strData and _type data members' memory are handled automatically by the compiler and their own destructors. The destructor of cocos2d::Value is responsible for deallocating all the resources of pointer member variables(_vectorData,_mapData and _intKeyMapData).

WARNING: cocos2d::Value doesn't use retain/release and refcount memory management like other cocos2d classes!

Basic Usage

The usage of cocos2d::Value is very straightforward.

Here is a simple usage example:

 
 

  
  
 
   
 
    
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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 = new Vector<Object*>();
vecV->pushBack(sp0);
Value val3(vecV);   // initialize with Vector
log("The description of the Vector value:%s",val3.getDescription().c_str());
delete vecV;
//----------------------------------------------------
Map<std::string,Object*>* mapV = new Map<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());
delete mapV;
//----------------------------------------------------
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());
 
   
 
  
 
 

output:

 
 

  
  
 
   
 
    
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cocos2d: val is null
cocos2d: The description of the integer value:
65

cocos2d: val1.asByte() = A
cocos2d: The description of the string value:
string

cocos2d: The description of the Vector value:
true

cocos2d: The description of the Map value:
true

cocos2d: The description of the Value-type value:
true

cocos2d: operator-> The description of val2:
65

cocos2d: operator-> The description of val4:
4
 
   
 
  
 
 

Best Practice

• Prefer cocos2d::Value and new template container(cocos2d::Vector<T> and cocos2d::Map<K,V>) over cocos2d::CCBool,cocos2d::CCFloat,cocos2d::CCDouble,cocos2d::CCString,cocos2d::CCInteger and old Objective-c style container(cocos2d::CCArray and cocos2d::CCDictionary).
• When you want to deal with primitives aggregate,wrap the primitives with cocos2d::Value and combine them with the new template container cocos2d::Vector<T> and cocos2d::Map<K,V>.

（编辑：李大同）

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