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<li><a class="el" href="index.html">Soprano (aka QRDF) - A modular RDF storage framework</a> </li>
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<h1>Error handling in <a class="el" href="namespaceSoprano.html">Soprano</a> </h1> </div>
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<p>Soprano tries to simulate exceptions through the usage of <a class="el" href="classSoprano_1_1Error_1_1ErrorCache.html" title="Core class of Soprano's exception system.">Soprano::Error::ErrorCache</a>.</p>
<p>Most methods in Soprano classes have a means of reporting if an operation was successful or not. For additional error information they inherit <a class="el" href="classSoprano_1_1Error_1_1ErrorCache.html" title="Core class of Soprano's exception system.">Soprano::Error::ErrorCache</a> which provides the method <a class="el" href="classSoprano_1_1Error_1_1ErrorCache.html#a3251b8052cdf932d59a523ca215d21c9">Soprano::Error::ErrorCache::lastError()</a>.</p>
<p>Thus, advanced error handling would look as follows:</p>
<div class="fragment"><pre class="fragment"> <a class="code" href="classSoprano_1_1Model.html" title="A Model is the central class in Soprano. It is a queryable collection of RDF quadruples, i.e statements.">Soprano::Model</a>* model = <a class="code" href="namespaceSoprano.html#a66f765cf9fd9aae07f874fdb8867dd1c">Soprano::createModel</a>();
<a class="code" href="classSoprano_1_1Statement.html" title="A Statement instance represents one RDF quadruple.">Soprano::Statement</a> invalidStatement;
<span class="keywordflow">if</span>( model-><a class="code" href="classSoprano_1_1Model.html#aed5b923235288fbac997850cca8f6053">addStatement</a>( invalidStatement ) != Error::ErrorNone ) {
showErrorMessage( model-><a class="code" href="classSoprano_1_1Error_1_1ErrorCache.html#a3251b8052cdf932d59a523ca215d21c9">lastError</a>().message() );
}
</pre></div><p>For methods that do not return an immediate error status, <a class="el" href="classSoprano_1_1Error_1_1Error.html" title="Represents an error in Soprano.">Soprano::Error::Error</a> evaluates to a boolean. Thus, one can easily check if an error occurred as follows:</p>
<div class="fragment"><pre class="fragment"> <a class="code" href="classSoprano_1_1StatementIterator.html" title="An iterator that provides a stream of Statements.">Soprano::StatementIterator</a> it = model-><a class="code" href="classSoprano_1_1Model.html#a7f50dc6483e0bed7830877182c7906ac">listStatements</a>();
<span class="keywordflow">while</span>( it.<a class="code" href="classSoprano_1_1Iterator.html#a1ba632f6f015242ab9441da77d48415b">next</a>() ) {
doSomething( *it );
}
<span class="keywordflow">if</span>( it.<a class="code" href="classSoprano_1_1Error_1_1ErrorCache.html#a3251b8052cdf932d59a523ca215d21c9">lastError</a>() ) {
displayError( <span class="stringliteral">"Iteration failed: "</span> + it.<a class="code" href="classSoprano_1_1Error_1_1ErrorCache.html#a3251b8052cdf932d59a523ca215d21c9">lastError</a>().message() );
}
</pre></div><p>This has the same effect as checking for <a class="el" href="namespaceSoprano_1_1Error.html#aef1bd25c5b6705951735e0fb5c5ff525a69f521a4f40b463680d393963d5b4187">Soprano::Error::ErrorNone</a>.</p>
<p>This error handling is thread-safe. Thus, two threads can for example call methods of one Model at the same time and still get proper <a class="el" href="classSoprano_1_1Error_1_1Error.html" title="Represents an error in Soprano.">Soprano::Error::Error</a> instances back. </p>
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