\hypertarget{classElemNull}{
\section{ElemNull Class Reference}
\label{classElemNull}\index{ElemNull@{ElemNull}}
}


An element representing nothing.  




{\ttfamily \#include $<$elem\_\-null.hh$>$}

Inheritance diagram for ElemNull:\begin{figure}[H]
\begin{center}
\leavevmode
\includegraphics[height=2.000000cm]{classElemNull}
\end{center}
\end{figure}
\subsection*{Public Member Functions}
\begin{DoxyCompactItemize}
\item 
\hypertarget{classElemNull_ad2ccae6cd6d1b54c4f6b883b7a5af52b}{
{\bfseries ElemNull} (const char $\ast$)}
\label{classElemNull_ad2ccae6cd6d1b54c4f6b883b7a5af52b}

\item 
string \hyperlink{classElemNull_aa14ed02d17a69168f141732532c08615}{str} () const 
\begin{DoxyCompactList}\small\item\em Every element must be representable by a string. \item\end{DoxyCompactList}\item 
const char $\ast$ \hyperlink{classElemNull_a534d6f5a0f4af7f72751423ea539c26e}{type} () const 
\end{DoxyCompactItemize}
\subsection*{Static Public Attributes}
\begin{DoxyCompactItemize}
\item 
\hypertarget{classElemNull_a91e023341bc0fd7fe8afac323b3d6410}{
static const char $\ast$ {\bfseries id} = \char`\"{}null\char`\"{}}
\label{classElemNull_a91e023341bc0fd7fe8afac323b3d6410}

\item 
\hypertarget{classElemNull_a646b79042f792a8db0e8037c5c3c3dac}{
static Hash {\bfseries \_\-hash} = HASH\_\-ELEM\_\-NULL}
\label{classElemNull_a646b79042f792a8db0e8037c5c3c3dac}

\end{DoxyCompactItemize}


\subsection{Detailed Description}
An element representing nothing. Null.

This is used by \hyperlink{classVarRW}{VarRW} when an element being read is not available. For example, if \hyperlink{protocolthe-p}{the} route is \hyperlink{classIPv4}{IPv4}, but \hyperlink{protocolthe-p}{the} \hyperlink{classIPv6}{IPv6} representation is being asked for.

The dispatcher also treats Null arguments as a special case by returning a Null. 

\subsection{Member Function Documentation}
\hypertarget{classElemNull_aa14ed02d17a69168f141732532c08615}{
\index{ElemNull@{ElemNull}!str@{str}}
\index{str@{str}!ElemNull@{ElemNull}}
\subsubsection[{str}]{\setlength{\rightskip}{0pt plus 5cm}string ElemNull::str (
\begin{DoxyParamCaption}
{}
\end{DoxyParamCaption}
) const\hspace{0.3cm}{\ttfamily  \mbox{[}inline, virtual\mbox{]}}}}
\label{classElemNull_aa14ed02d17a69168f141732532c08615}


Every element must be representable by a string. 

This is a requirement to enable \hyperlink{protocolthe-p}{the} policy manager to send elements to \hyperlink{protocolthe-p}{the} backend filters via XRL calls for example.

\begin{DoxyReturn}{Returns}
string representation of \hyperlink{protocolthe-p}{the} element. 
\end{DoxyReturn}


Implements \hyperlink{classElement_a1acf1c63bbe1374c574bf19e3a000552}{Element}.

\hypertarget{classElemNull_a534d6f5a0f4af7f72751423ea539c26e}{
\index{ElemNull@{ElemNull}!type@{type}}
\index{type@{type}!ElemNull@{ElemNull}}
\subsubsection[{type}]{\setlength{\rightskip}{0pt plus 5cm}const char$\ast$ ElemNull::type (
\begin{DoxyParamCaption}
{}
\end{DoxyParamCaption}
) const\hspace{0.3cm}{\ttfamily  \mbox{[}inline, virtual\mbox{]}}}}
\label{classElemNull_a534d6f5a0f4af7f72751423ea539c26e}
\begin{DoxyReturn}{Returns}
string representation of element type. 
\end{DoxyReturn}


Implements \hyperlink{classElement_a17396c7d64fd4fc15713d3d803b57a56}{Element}.



The documentation for this class was generated from the following files:\begin{DoxyCompactItemize}
\item 
/home/greearb/git/xorp.ct.github/xorp/policy/common/elem\_\-null.hh\item 
/home/greearb/git/xorp.ct.github/xorp/policy/common/element.cc\end{DoxyCompactItemize}
