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| 2 | <!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/tutorial2.doc:969 -->
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| 3 | <html>
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| 4 | <head>
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| 5 | <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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| 6 | <title>File Handling</title>
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| 16 | <table border="0" cellpadding="0" cellspacing="0" width="100%">
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| 17 | <tr bgcolor="#E5E5E5">
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| 18 | <td valign=center>
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| 19 | <a href="index.html">
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| 20 | <font color="#004faf">Home</font></a>
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| 21 | | <a href="classes.html">
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| 22 | <font color="#004faf">All Classes</font></a>
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| 23 | | <a href="mainclasses.html">
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| 24 | <font color="#004faf">Main Classes</font></a>
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| 25 | | <a href="annotated.html">
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| 26 | <font color="#004faf">Annotated</font></a>
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| 27 | | <a href="groups.html">
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| 28 | <font color="#004faf">Grouped Classes</font></a>
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| 29 | | <a href="functions.html">
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| 30 | <font color="#004faf">Functions</font></a>
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| 31 | </td>
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| 32 | <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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| 33 |
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| 34 |
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| 35 | <p>
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| 36 | <p> (Extracts from <tt>chartform_files.cpp</tt>.)
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| 37 | <p> <h2> Reading Chart Data
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| 38 | </h2>
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| 39 | <a name="1"></a><p>
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| 40 |
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| 41 | <pre> void ChartForm::load( const <a href="qstring.html">QString</a>& filename )
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| 42 | {
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| 43 | <a href="qfile.html">QFile</a> file( filename );
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| 44 | if ( !file.<a href="qfile.html#open">open</a>( <a href="qfile.html#open">IO_ReadOnly</a> ) ) {
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| 45 | <a href="qmainwindow.html#statusBar">statusBar</a>()->message( QString( "Failed to load \'%1\'" ).
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| 46 | arg( filename ), 2000 );
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| 47 | return;
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| 48 | }
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| 49 |
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| 50 | init(); // Make sure we have colours
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| 51 | m_filename = filename;
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| 52 | <a href="qtextstream.html">QTextStream</a> ts( &file );
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| 53 | Element element;
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| 54 | int errors = 0;
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| 55 | int i = 0;
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| 56 | <a name="x2592"></a> while ( !ts.<a href="qtextstream.html#eof">eof</a>() ) {
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| 57 | ts >> element;
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| 58 | if ( element.isValid() )
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| 59 | m_elements[i++] = element;
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| 60 | </pre><pre> <a name="x2590"></a> file.<a href="qfile.html#close">close</a>();
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| 61 | </pre>
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| 62 | <p> <pre> <a href="qwidget.html#setCaption">setCaption</a>( QString( "Chart -- %1" ).arg( filename ) );
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| 63 | updateRecentFiles( filename );
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| 64 |
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| 65 | drawElements();
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| 66 | m_changed = FALSE;
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| 67 | }
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| 68 | </pre>
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| 69 | <p> Loading a data set is very easy. We open the file and create a text
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| 70 | 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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| 71 | All the detail is handled by the <tt>Element</tt> class. Then we close
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| 72 | the file and update the caption and the recent files list. Finally we
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| 73 | draw the chart and mark it as unchanged.
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| 74 | <p> <h2> Writing Chart Data
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| 75 | </h2>
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| 76 | <a name="2"></a><p> <pre> void ChartForm::fileSave()
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| 77 | {
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| 78 | </pre><pre> <a href="qfile.html">QFile</a> file( m_filename );
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| 79 | <a name="x2591"></a> if ( !file.<a href="qfile.html#open">open</a>( <a href="qfile.html#open">IO_WriteOnly</a> ) ) {
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| 80 | <a href="qmainwindow.html#statusBar">statusBar</a>()->message( QString( "Failed to save \'%1\'" ).
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| 81 | arg( m_filename ), 2000 );
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| 82 | return;
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| 83 | }
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| 84 | <a href="qtextstream.html">QTextStream</a> ts( &file );
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| 85 | for ( int i = 0; i < MAX_ELEMENTS; ++i )
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| 86 | if ( m_elements[i].isValid() )
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| 87 | ts << m_elements[i];
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| 88 |
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| 89 | file.<a href="qfile.html#close">close</a>();
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| 90 |
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| 91 | <a href="qwidget.html#setCaption">setCaption</a>( QString( "Chart -- %1" ).arg( m_filename ) );
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| 92 | <a href="qmainwindow.html#statusBar">statusBar</a>()->message( QString( "Saved \'%1\'" ).arg( m_filename ), 2000 );
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| 93 | m_changed = FALSE;
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| 94 | }
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| 95 | </pre>
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| 96 | <p> Saving data is equally easy. We open the file and create a text
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| 97 | stream. We then stream every valid element to the text stream. All the
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| 98 | detail is handled by the <tt>Element</tt> class.
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| 99 | <p> <p align="right">
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| 100 | <a href="tutorial2-06.html">« Canvas Control</a> |
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| 101 | <a href="tutorial2.html">Contents</a> |
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| 102 | <a href="tutorial2-08.html">Taking Data »</a>
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| 103 | </p>
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| 104 | <p>
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| 105 | <!-- eof -->
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| 106 | <p><address><hr><div align=center>
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| 107 | <table width=100% cellspacing=0 border=0><tr>
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| 108 | <td>Copyright © 2007
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| 109 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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| 110 | <td align=right><div align=right>Qt 3.3.8</div>
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| 111 | </table></div></address></body>
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| 112 | </html>
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