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<a href="#pub-static-methods">Static Public Member Functions</a> </div>
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<div class="title">Wt::Dbo::sql_value_traits< V, Enable > Class Template Reference<div class="ingroups"><a class="el" href="group__dbo.html">Database Objects (Wt::Dbo)</a></div></div> </div>
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<p>Traits class for value types.
<a href="structWt_1_1Dbo_1_1sql__value__traits.html#details">More...</a></p>
<p><code>#include <Wt/Dbo/SqlTraits></code></p>
<p><a href="classWt_1_1Dbo_1_1sql__value__traits-members.html">List of all members.</a></p>
<table class="memberdecls">
<tr><td colspan="2"><h2><a name="pub-static-methods"></a>
Static Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static const char * </td><td class="memItemRight" valign="bottom"><a class="el" href="structWt_1_1Dbo_1_1sql__value__traits.html#a938ffa7506a84bf46fa6e9a4d3c69253">type</a> (<a class="el" href="classWt_1_1Dbo_1_1SqlConnection.html">SqlConnection</a> *connection, int size)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Returns the SQL type name. <a href="#a938ffa7506a84bf46fa6e9a4d3c69253"></a><br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static void </td><td class="memItemRight" valign="bottom"><a class="el" href="structWt_1_1Dbo_1_1sql__value__traits.html#aeed1a933f3d83555b5d39ac76b929170">bind</a> (const V &v, <a class="el" href="classWt_1_1Dbo_1_1SqlStatement.html">SqlStatement</a> *statement, int index, int size)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Binds a value to a statement parameter. <a href="#aeed1a933f3d83555b5d39ac76b929170"></a><br/></td></tr>
<tr><td class="memItemLeft" align="right" valign="top">static bool </td><td class="memItemRight" valign="bottom"><a class="el" href="structWt_1_1Dbo_1_1sql__value__traits.html#ab3c8e4555b710451a3793059734fc751">read</a> (V &v, <a class="el" href="classWt_1_1Dbo_1_1SqlStatement.html">SqlStatement</a> *statement, int column, int size)</td></tr>
<tr><td class="mdescLeft"> </td><td class="mdescRight">Reads a result from an executed query. <a href="#ab3c8e4555b710451a3793059734fc751"></a><br/></td></tr>
</table>
<hr/><a name="details" id="details"></a><h2>Detailed Description</h2>
<div class="textblock"><h3>template<typename V, class Enable = void><br/>
class Wt::Dbo::sql_value_traits< V, Enable ></h3>
<p>Traits class for value types. </p>
<p>This traits class may be specialized for a custom type <code>V</code>, to add dbo support for custom types. A value type has a one-to-one mapping to a single database column.</p>
<p>The library has built-in support for:</p>
<ul>
<li><code>std::string</code></li>
<li><code>char const *</code> (read-only: only as a bound parameter for a query)</li>
<li><code>short</code>, <code>int</code>, <code>long long</code></li>
<li><code>long</code>: since the size of a <code>long</code> is 64bit on UNIX/Linux 64bit systems and 32bit otherwise, it is mapped to an <code>integer</code> or a <code>bigint</code> depending on the environment.</li>
<li><code>float</code>, <code>double</code></li>
<li>enum types</li>
<li><code>bool</code></li>
<li><code>std::vector<unsigned char></code> (binary data)</li>
<li><code>boost::optional<T></code>: to make the type optional (allowing an SQL <code>null</code> value)</li>
<li><code>boost::posix_time::ptime</code>: time stamp, an invalid value (e.g. default constructed), maps to <code>null</code></li>
<li><code>boost::posix_time::time_duration</code>: time interval, an invalid value (boost::posix_time::not_a_date_time), maps to <code>null</code></li>
</ul>
<p>In <Wt/Dbo/WtSqlTraits>, traits classes are also provided for:</p>
<ul>
<li><a class="el" href="classWt_1_1WDate.html" title="A value class that represents a date on the Gregorian calendar.">WDate</a></li>
<li><a class="el" href="classWt_1_1WDateTime.html" title="A calendar date and clock time.">WDateTime</a></li>
<li><a class="el" href="classWt_1_1WTime.html" title="A value class that defines a clock time.">WTime</a></li>
<li><a class="el" href="classWt_1_1WString.html" title="A value class which describes a locale-aware unicode string.">WString</a></li>
</ul>
<dl class="see"><dt><b>See also:</b></dt><dd><a class="el" href="structWt_1_1Dbo_1_1query__result__traits.html" title="Traits class for result types.">query_result_traits</a> </dd></dl>
</div><hr/><h2>Member Function Documentation</h2>
<a class="anchor" id="aeed1a933f3d83555b5d39ac76b929170"></a><!-- doxytag: member="Wt::Dbo::sql_value_traits::bind" ref="aeed1a933f3d83555b5d39ac76b929170" args="(const V &v, SqlStatement *statement, int index, int size)" -->
<div class="memitem">
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<div class="memtemplate">
template<typename V, class Enable = void> </div>
<table class="memname">
<tr>
<td class="memname">static void <a class="el" href="structWt_1_1Dbo_1_1sql__value__traits.html">Wt::Dbo::sql_value_traits</a>< V, Enable >::bind </td>
<td>(</td>
<td class="paramtype">const V & </td>
<td class="paramname"><em>v</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classWt_1_1Dbo_1_1SqlStatement.html">SqlStatement</a> * </td>
<td class="paramname"><em>statement</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>index</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>size</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td><code> [static]</code></td>
</tr>
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</div>
<div class="memdoc">
<p>Binds a value to a statement parameter. </p>
<p>The value <code>v</code> must be bound to parameter with index <code>index</code> in the <code>statement</code>.</p>
<dl class="see"><dt><b>See also:</b></dt><dd><a class="el" href="classWt_1_1Dbo_1_1SqlStatement.html#ad8b53ca87bdef11ceceb96ab05c260b9" title="Binds a value to a column.">SqlStatement::bind()</a> </dd></dl>
</div>
</div>
<a class="anchor" id="ab3c8e4555b710451a3793059734fc751"></a><!-- doxytag: member="Wt::Dbo::sql_value_traits::read" ref="ab3c8e4555b710451a3793059734fc751" args="(V &v, SqlStatement *statement, int column, int size)" -->
<div class="memitem">
<div class="memproto">
<div class="memtemplate">
template<typename V, class Enable = void> </div>
<table class="memname">
<tr>
<td class="memname">static bool <a class="el" href="structWt_1_1Dbo_1_1sql__value__traits.html">Wt::Dbo::sql_value_traits</a>< V, Enable >::read </td>
<td>(</td>
<td class="paramtype">V & </td>
<td class="paramname"><em>v</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="classWt_1_1Dbo_1_1SqlStatement.html">SqlStatement</a> * </td>
<td class="paramname"><em>statement</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>column</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>size</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td><code> [static]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Reads a result from an executed query. </p>
<p>The value <code>v</code> must be read from result column <code>column</code> in the <code>statement</code>.</p>
<p>Returns <code>true</code> if the value was not <code>null</code>. This result may be used by the boost::optional<V> specialization to support fields that may have <code>null</code> values.</p>
<dl class="see"><dt><b>See also:</b></dt><dd><a class="el" href="classWt_1_1Dbo_1_1SqlStatement.html#afca829eb43f0977b2af6ea7e0b66aad1" title="Fetches a result value.">SqlStatement::getResult()</a> </dd></dl>
</div>
</div>
<a class="anchor" id="a938ffa7506a84bf46fa6e9a4d3c69253"></a><!-- doxytag: member="Wt::Dbo::sql_value_traits::type" ref="a938ffa7506a84bf46fa6e9a4d3c69253" args="(SqlConnection *connection, int size)" -->
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<div class="memproto">
<div class="memtemplate">
template<typename V, class Enable = void> </div>
<table class="memname">
<tr>
<td class="memname">static const char* <a class="el" href="structWt_1_1Dbo_1_1sql__value__traits.html">Wt::Dbo::sql_value_traits</a>< V, Enable >::type </td>
<td>(</td>
<td class="paramtype"><a class="el" href="classWt_1_1Dbo_1_1SqlConnection.html">SqlConnection</a> * </td>
<td class="paramname"><em>connection</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>size</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td><code> [static]</code></td>
</tr>
</table>
</div>
<div class="memdoc">
<p>Returns the SQL type name. </p>
<p>The <code>size</code> (for strings) is a hint and may be ignored by a back-end.</p>
<p>This will usually return a type ending with " not null" except for C++ types that support <code>null</code> values. For a normal c++ value type <code>T</code>, boost::optional<T> has been specialized to allow for <code>null</code> values. </p>
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