mutable-data-members-cpp.md

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Mutable Data Members (C++) | Microsoft Docs		11/04/2016	cpp-language	language-reference	mutable_cpp	C++	mutable keyword [C++]	ebe89746-3d36-43a8-8d69-f426af23f551	mikeblome	mblome	cplusplus

Mutable Data Members (C++)

This keyword can only be applied to non-static and non-const data members of a class. If a data member is declared mutable, then it is legal to assign a value to this data member from a const member function.

Syntax

mutable member-variable-declaration;  

Remarks

For example, the following code will compile without error because m_accessCount has been declared to be mutable, and therefore can be modified by GetFlag even though GetFlag is a const member function.

// mutable.cpp  
class X  
{  
public:  
   bool GetFlag() const  
   {  
      m_accessCount++;  
      return m_flag;  
   }  
private:  
   bool m_flag;  
   mutable int m_accessCount;  
};  
  
int main()  
{  
}  

See also

Keywords