mutable.tex

\subsection{mutable}

\begin{frame}[fragile]{const aushebeln}

\begin{block}{mutable}
\begin{small}
	\begin{lstlisting}[language=C++]
class MyClass
{
private:
    mutable unsigned int m_uCounter;
public:
    unsigned int getCounter() const
    {
        return this->m_uCounter;
    }
    
    int compute(int value) const
    {
      m_uCounter++;
      return value*42;
    }
};
	\end{lstlisting}
	\end{small}
\end{block}

\end{frame}

\subsection{const cast}

\begin{frame}[fragile]{const aushebeln}

\begin{block}{mutable}
\begin{small}
	\begin{lstlisting}[language=C++]
MyClass test;
const MyClass& const_test = test;

std::cout << test.compute(1)        << std::endl;
std::cout << test.compute(-3)       << std::endl;
std::cout << const_test.compute(-5) << std::endl;
std::cout << test.getCounter()      << std::endl; // gibt 3 aus
	\end{lstlisting}
	\end{small}
\end{block}

\end{frame}

\begin{frame}[fragile]{const aushebeln}

\begin{block}{mutable}
\begin{small}
	\begin{lstlisting}[language=C++]
void bad_function(const int& const_ref)
{
    const_ref++; // kompiliert nicht
    int& ref = const_cast<int&>(const_ref);
    ref++;       // kompiliert
}

int original = 5;
bad_function(original);
std::cout << original << std::endl; // gibt 6 aus
	\end{lstlisting}
	\end{small}
\end{block}

\end{frame}