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<title>InsVal</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>InsVal</h1>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td><img src="functors.gif" width="194" height="38"></td>
<td align="right"><img src="concept.gif" width="194"
height="39"></td>
</tr>
<tr>
<td valign="top"><b>Category</b>: functors</td>
<td align="right" valign="top"><b>Component type</b>:
concept</td>
</tr>
</table>
<h3>Description</h3>
<p><font size="2" face="Courier New">InsVal </font>is a function object (this can be a wrapped function pointer if you use
<a href="cb_ptr_fun.htm"> <font size="2" face="Courier New">cb_ptr_fun_w_ret()</font></a>) that is
called to to validate a user defined <font size="2"
face="Courier New">DataObj</font> before it is inserted into the
database. The function returns <font size="2" face="Courier New">true</font>
if the <font size="2" face="Courier New">DataObj</font> contains
a valid set of fields, <font size="2" face="Courier New">false</font>
otherwise. <font size="2" face="Courier New">InsVal</font> is
called on each record inserted or updated into the database via
either <a href="DBView.htm"><font size="2"
face="Courier New">DBView</font></a> or <a
href="IndexedDBView.htm"><font size="2"
face="Courier New">IndexedDBView</font></a><font size="2"
face="Courier New">. </font>The default behavior of a <font
size="2" face="Courier New">InsVal </font>can be found in the<font
size="2" face="Courier New"> DefaultInsValidate<DataObj></font>
template. This functor always assumes the object is valid and
thus returns<font size="2" face="Courier New"> true</font> .
Through the use of template specialization, you can customize the
default behavior for this functor by writing your own <font
size="2" face="Courier New">DefaultInsValidate<DataObj> </font>for
that class of <font size="2" face="Courier New">DataObj's.</font></p>
<h3>Refinement of</h3>
<p>None.</p>
<h3>Associated types</h3>
<p><a href="BoundIO.htm"><font size="2" face="Courier New">BoundIOs</font></a><font
size="2" face="Courier New">.</font></p>
<h3>Example 1:</h3>
<pre><code><span class="codeComment">//Default InsVal function
// Insertion is by default, always valid.
// If any RI constraints are violated,
// DB will return errors when the actual insert is performed
// which occurs after InsValidate returns.
// If there are certain business rule constraints you wish to enforce, put them in
// your own InsValidate functor.
// You can also specialize this template if you wish to have different default behavior
// for your data class.</span>
template<class DataObj> class DefaultInsValidate {
public:
bool operator()(DataObj &rowbuf)
{
return true;
}
};
</code></pre>
<h3>Example 2:</h3>
<pre><code><span class="codeComment">// Enforce business rule for inserted rows</span>
class Example
{
public: <span class="codeComment">// tablename.columnname:</span>
int exampleInt; <span class="codeComment">// DB_EXAMPLE.INT_VALUE</span>
string exampleStr; <span class="codeComment">// DB_EXAMPLE.STRING_VALUE</span>
double exampleDouble; <span class="codeComment">// DB_EXAMPLE.DOUBLE_VALUE</span>
long exampleLong; <span class="codeComment">// DB_EXAMPLE.EXAMPLE_LONG</span>
TIMESTAMP_STRUCT exampleDate; <span class="codeComment">// DB_EXAMPLE.EXAMPLE_DATE</span>
};
<span class="codeComment">// specialization of DefaultInsValidate for Example
// can have any number of InsValidate functions for a single data class just as with
// ParamObj's ... below is general business rule constraint we wish to enforce for all Examples</span>
template<> class dtl::DefaultInsValidate<Example> {
public:
bool operator()(Example &rowbuf)
{
<span class="codeComment">// data is valid if rowbuf.exampleStr is nonempty and rowbuf.exampleDouble is
// between 0 and 100 (like a percentage)</span>
return (rowbuf.exampleStr.length() > 0 && rowbuf.exampleDouble >= 0.0 &&
rowbuf.exampleLong <= 100.0);
}
};
</code></pre>
<p> </p>
<h3>Notation</h3>
<table border="0">
<tr>
<td valign="top"><tt>X</tt> </td>
<td valign="top">A type that is a model of<font size="2"
face="Courier New"> InsVal</font></td>
</tr>
<tr>
<td valign="top"><tt>a</tt> </td>
<td valign="top">Object of type <tt>X</tt> </td>
</tr>
</table>
<h3>Expression semantics</h3>
<table border="1">
<tr>
<th>Name </th>
<th>Expression </th>
<th>Precondition </th>
<th>Semantics </th>
<th>Postcondition </th>
</tr>
<tr>
<td valign="top">Default constructor </td>
<td valign="top"><pre>X a()</pre>
</td>
<td valign="top"> </td>
<td valign="top">Construct the function object.</td>
<td valign="top"> </td>
</tr>
<tr>
<td valign="top">Copy constructor </td>
<td valign="top"><pre>X a(const X &b)</pre>
</td>
<td valign="top"> </td>
<td valign="top">Copy construct the<font size="2"
face="Courier New"> InsVal.</font>.</td>
<td valign="top"> </td>
</tr>
<tr>
<td valign="top">Assignment operator</td>
<td valign="top"><pre>X& operator=(const X&b)</pre>
</td>
<td valign="top"> </td>
<td valign="top">Assignment copy</td>
<td valign="top"> </td>
</tr>
<tr>
<td valign="top">Validate operator</td>
<td valign="top"><pre>void operator()(DataObj &rowbuf)</pre>
</td>
<td valign="top"> </td>
<td valign="top">This operator takes a reference to a <font
size="2" face="Courier New">rowbuf </font>holding a user
defined data object. The job of the operator is to
validate this <font size="2" face="Courier New">DataObj</font>.
On exit, the operator should return <font size="2"
face="Courier New">true </font>if it was able to validate
the data object, <font size="2" face="Courier New">false</font>
otherwise.</td>
<td valign="top">The fields in <font size="2"
face="Courier New">DataObj </font>should contain valid
values if the function returns <font size="2"
face="Courier New">true</font>.</td>
</tr>
</table>
<h3>Notes</h3>
<p>None.</p>
<h3>See also</h3>
<p><a href="BoundIO.htm"><font size="2" face="Courier New">BoundIOs</font></a><font
size="2" face="Courier New">, </font><a href="BCA.htm"><font
size="2" face="Courier New">BCA</font></a><font size="2"
face="Courier New">, </font><a href="BPA.htm"><font size="2"
face="Courier New">BPA</font></a><font size="2"
face="Courier New">, </font><a href="DBView.htm"><font
size="2" face="Courier New">DBView</font></a><font size="2"
face="Courier New">, </font><a
href="IndexedDBView.htm"><font size="2"
face="Courier New">IndexedDBView</font><font size="2"><!--start footer--></font></a></p>
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