📄 variantexception.htm
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<title>VariantException</title>
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<p><font size="6" face="Bookman Old Style"><em><strong><u>dtl</u></strong></em></font></p>
<p><img src="stat.gif" width="6" height="6"> <!--end header--> <br>
</p>
<h1>VariantException</h1>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td><img src="exceptions.gif" width="194" height="38"></td>
<td align="right"><img src="type.gif" width="194"
height="39"></td>
</tr>
<tr>
<td valign="top"><b>Category</b>: exceptions</td>
<td align="right" valign="top"><b>Component type</b>:
type</td>
</tr>
</table>
<h3>Description</h3>
<p><tt>VariantException</tt> is thrown by the variant classes in
the DTL, usually when a variant cannot internally be converted
from one type to another or when a variant object receives an
object of a type it does not know how to handle. An exception of
this type stores strings representing which method the exception
was thrown in and a message describing what error occurred. The
call to the constructor initializes these strings. The user can
extract a stringified message with all of this information from
the exception using the standard <font size="2"
face="Courier New">what() </font><font size="3">method.</font></p>
<h3>Definition</h3>
<p>Defined in the <font size="2" face="Courier New">VariantException.h</font><font
size="1" face="Courier New"> </font>header file. </p>
<h3>Example: Trivial case of throwing and catching a
VariantException</h3>
<p><code>class UnknownToVariant<br>
{ <br>
};<br>
<br>
void IWillThrow()<br>
{ <br>
variant_t v = UnknownToVariant(); <span class="codeComment">// create a
variant using a type that variant_t can't convert</span><br>
char *str = v; <span class="codeComment">// unknown conversion will cause
this statement to throw a VariantException</span><br>
}<br>
<br>
<br>
int main()<br>
{<br>
try<br>
{<br>
<span class="codeComment">// call our method which
throws</span><br>
IWillThrow();<br>
}<br>
catch (RootException &ex)<br>
{<br>
<span class="codeComment">// can also say: cout
<< ex << endl;</span><br>
<span class="codeComment">// operator<<() for
RootExceptions just streams out what()</span><br>
cout << ex.what()
<< endl;<br>
}<br>
return 0; <span class="codeComment">// won't reach here ... exception
thrown above</span><br>
}</code></p>
<h3>Model of</h3>
<p>Standard C++ library exception.</p>
<h3>Public base classes</h3>
<p><font size="2" face="Courier New">RootException</font></p>
<h3>Members</h3>
<table border="2">
<tr>
<th>Member </th>
<th>Where defined </th>
<th>Description </th>
</tr>
<tr>
<td valign="top"><font size="2" face="Courier New">VariantException(const
string &meth, const string &err)</font></td>
<td valign="top"><tt>VariantException</tt> </td>
<td valign="top">Constructor which takes a specific
method and error string.</td>
</tr>
<tr>
<td valign="top"><font size="2" face="Courier New">virtual
const char* what() const throw()</font></td>
<td valign="top"><tt>RootException</tt> </td>
<td valign="top">Overrides behavior in <font size="2"
face="Courier New">std::exception. </font><font size="3">Returns
a C string describing the exception, including the method
it was thrown in, the error message describing why it was
thrown, and what type of exception was thrown. Subclasses
do and may override </font><font size="2"
face="Courier New">what() </font>based on their needs. <font
size="3">See Note </font><a href="RootException.htm#1"><font
size="3">[1]</font></a><font size="3"> in class </font><a
href="RootException.htm"><font size="2"
face="Courier New">RootException</font></a><font size="3">.</font></td>
</tr>
<tr>
<td valign="top"><tt>friend ostream &operator<<(ostream
&o, const RootException &ex)</tt></td>
<td valign="top"><tt>RootException</tt> </td>
<td valign="top">Note that this is a friend function, and
not a member. Streams out <font size="2"
face="Courier New">ex.what()</font><font size="3"> to </font><font
size="2" face="Courier New">o.</font><font size="3"> As </font><font
size="2" face="Courier New">what() </font><font size="3">is
virtual, the appropriate version of that method will be
called for </font><font size="2" face="Courier New">ex.</font></td>
</tr>
</table>
<h3>Notes</h3>
<p>None.<font size="3"><tt><br>
</tt></font></p>
<h3>See also</h3>
<p><a href="RootException.htm"><font size="2" face="Courier New">RootException</font></a>.<br>
<br>
</p>
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