📄 delete_iterator.htm
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<title>DBView<DataObj,ParamObj>::delete_iterator</title>
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<p><font size="6" face="Bookman Old Style"><em><strong><u>dtl</u></strong></em></font></p>
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<h1>DBView<DataObj, ParamObj>::delete_iterator</h1>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td><img src="iterator.gif" width="194" height="38"></td>
<td align="right"><img src="type.gif" width="194"
height="39"></td>
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<tr>
<td valign="top"><b>Category</b>: iterators</td>
<td align="right" valign="top"><b>Component type</b>:
type</td>
</tr>
</table>
<h3>Description</h3>
<p><tt>DBView<DataObj, ParamObj>::delete_iterator</tt> is
an <a href="http://www.sgi.com/tech/stl/OutputIterator.html">Output
Iterator</a> that performs the deletion of objects of type <font
size="2" face="Courier New">DataObj</font> from a particular <font
size="2" face="Courier New">DBView</font><font size="2"> </font>(and
thus the database). The actual <font size="2" face="Courier New">DataObj
</font><font size="3">that the</font><font size="4"> </font><font
size="2" face="Courier New">delete_iterator</font><font size="2">
</font>references specifies the parameters of what <font size="2"
face="Courier New">DataObj's </font>to delete from the database.
To specify more parameters to refine the delete, define a <tt>ParamObj
</tt><font size="4" face="Times New Roman"><tt>and</tt></font><tt>
</tt><a href="BPA.htm"><tt>BPA</tt></a><tt> </tt>in the
underlying <tt>DBView</tt>. The <font size="2" face="Courier New">delete_iterator
</font>generates the following SQL statement to delete records
from the database: <font size="2" face="Courier New">"DELETE
FROM " + tablename_from_view + " WHERE " + "<field1_from_BCA>=(?)
AND <field2_from_BCA>=(?) AND ... " +
posfix_clause_from_view. </font><font size="3">The first set of
parameters in the </font><font size="2" face="Courier New">WHERE </font><font
size="3">clause from the</font><font size="2" face="Courier New">
</font><a href="BCA.htm"><tt>BCA</tt></a><font size="2"
face="Courier New"> </font><font size="3">will be automatically
bound to fields in the</font><font size="2" face="Courier New">
DataObj. </font><font size="3">These parameters are set
automatically upon assignment to the </font><font size="2"
face="Courier New">delete_iterator.</font><font size="3">
Any additional parameters in the postfix clause will be bound to
the</font><font size="2" face="Courier New"> ParamObj. </font>Note
that all of the restrictions of an <a
href="http://www.sgi.com/tech/stl/OutputIterator.html">Output
Iterator</a> must be obeyed, including the restrictions on the
ordering of <tt>operator*</tt> and <tt>operator++</tt> operations.
</p>
<h3>Definition</h3>
<p>Defined in the <font size="2" face="Courier New">delete_iterator.h</font>
header file. </p>
<h3>Example:</h3>
<p><pre><code><span class="codeComment">// Delete objects from the database via a delete_iterator</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>
Example(int exInt, const string &exStr, double exDouble, long exLong,
const TIMESTAMP_STRUCT &exDate) :
exampleInt(exInt), exampleStr(exStr), exampleDouble(exDouble), exampleLong(exLong),
exampleDate(exDate)
{ }
};
class BCAExampleObj
{
public:
void operator()(BoundIOs &boundIOs, Example &rowbuf)
{
boundIOs["INT_VALUE"] == rowbuf.exampleInt;
boundIOs["STRING_VALUE"] == rowbuf.exampleStr;
boundIOs["DOUBLE_VALUE"] == rowbuf.exampleDouble;
boundIOs["EXAMPLE_LONG"] == rowbuf.exampleLong;
boundIOs["EXAMPLE_DATE"] == rowbuf.exampleDate;
}
};
class ExampleParamObj
{
public:
int lowIntValue;
string strValue;
};
class BPAParamObj
{
public:
void operator()(BoundIOs &boundIOs, ExampleParamObj &paramObj)
{
boundIOs[0] == paramObj.strValue;
boundIOs[1] == paramObj.lowIntValue;
}
};
<span class="codeComment">// Delete rows matching the specified Example objects from the database</span>
void DeleteData()
{
<span class="codeComment">// construct view</span>
DBView<Example, ExampleParamObj>
view("DB_EXAMPLE", BCAExampleObj(), "OR STRING_VALUE = (?) OR INT_VALUE = (?)", BPAParamObj());
<span class="codeComment">// build a deleter for the view
// *** SQL Query Generated for this delete_iterator:" ***
// *** (Note: All column and field names that were generated by the BCA are alphabetized due to our implementation) ***
// "DELETE FROM DB_EXAMPLE WHERE EXAMPLE_DATE = (?) AND STRING_VALUE = (?) "
// "OR STRING_VALUE = (?) OR INT_VALUE = (?)"</span>
DBView<Example, ExampleParamObj, BCAExampleObj, BPAParamObj>::delete_iterator
exampleDeleter = view;
<span class="codeComment">// now set the parameters indicating which rows we want to delete</span>
exampleDeleter->exampleStr = "Example";
TIMESTAMP_STRUCT y2k = {2000, 1, 1, 0, 0, 0, 0};
exampleDeleter->exampleDate = y2k;
exampleDeleter.Params().strValue = "Find Me";
exampleDeleter.Params().lowIntValue = 18;
<span class="codeComment">// execute the delete</span>
exampleDeleter++;
cout << exampleDeleter.GetLastCount()
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