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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>File Handling</title>
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<td valign=center>
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<font color="#004faf">Main Classes</font></a>
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</td>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>File Handling</h1>
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<p>
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<p> (Extracts from <tt>chartform_files.cpp</tt>.)
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<p> <h2> Reading Chart Data
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</h2>
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<a name="1"></a><p>
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<pre> void ChartForm::load( const <a href="tqstring.html">TQString</a>& filename )
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{
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<a href="tqfile.html">TQFile</a> file( filename );
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if ( !file.<a href="tqfile.html#open">open</a>( <a href="tqfile.html#open">IO_ReadOnly</a> ) ) {
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<a href="tqmainwindow.html#statusBar">statusBar</a>()->message( TQString( "Failed to load \'%1\'" ).
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arg( filename ), 2000 );
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return;
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}
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init(); // Make sure we have colours
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m_filename = filename;
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<a href="tqtextstream.html">TQTextStream</a> ts( &file );
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Element element;
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int errors = 0;
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int i = 0;
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<a name="x2592"></a> while ( !ts.<a href="tqtextstream.html#eof">eof</a>() ) {
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ts >> element;
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if ( element.isValid() )
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m_elements[i++] = element;
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</pre><pre> <a name="x2590"></a> file.<a href="tqfile.html#close">close</a>();
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</pre>
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<p> <pre> <a href="tqwidget.html#setCaption">setCaption</a>( TQString( "Chart -- %1" ).arg( filename ) );
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updateRecentFiles( filename );
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drawElements();
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m_changed = FALSE;
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}
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</pre>
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<p> Loading a data set is very easy. We open the file and create a text
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stream. While there's data to read we stream an element into <tt>element</tt> and if it is valid we insert it into the <tt>m_elements</tt> vector.
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All the detail is handled by the <tt>Element</tt> class. Then we close
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the file and update the caption and the recent files list. Finally we
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draw the chart and mark it as unchanged.
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<p> <h2> Writing Chart Data
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</h2>
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<a name="2"></a><p> <pre> void ChartForm::fileSave()
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{
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</pre><pre> <a href="tqfile.html">TQFile</a> file( m_filename );
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<a name="x2591"></a> if ( !file.<a href="tqfile.html#open">open</a>( <a href="tqfile.html#open">IO_WriteOnly</a> ) ) {
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<a href="tqmainwindow.html#statusBar">statusBar</a>()->message( TQString( "Failed to save \'%1\'" ).
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arg( m_filename ), 2000 );
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return;
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}
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<a href="tqtextstream.html">TQTextStream</a> ts( &file );
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for ( int i = 0; i < MAX_ELEMENTS; ++i )
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if ( m_elements[i].isValid() )
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ts << m_elements[i];
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file.<a href="tqfile.html#close">close</a>();
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<a href="tqwidget.html#setCaption">setCaption</a>( TQString( "Chart -- %1" ).arg( m_filename ) );
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<a href="tqmainwindow.html#statusBar">statusBar</a>()->message( TQString( "Saved \'%1\'" ).arg( m_filename ), 2000 );
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m_changed = FALSE;
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}
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</pre>
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<p> Saving data is equally easy. We open the file and create a text
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stream. We then stream every valid element to the text stream. All the
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detail is handled by the <tt>Element</tt> class.
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<p> <p align="right">
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<a href="tutorial2-06.html">« Canvas Control</a> |
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<a href="tutorial2.html">Contents</a> |
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<a href="tutorial2-08.html">Taking Data »</a>
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</p>
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<p>
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<!-- eof -->
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>TQt 3.3.8</div>
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</table></div></address></body>
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</html>
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