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<title>File Handling</title>
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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>
<p>
<p> (Extracts from <tt>chartform_files.cpp</tt>.)
<p> <h2> Reading Chart Data
</h2>
<a name="1"></a><p>
<pre> void ChartForm::load( const <a href="ntqstring.html">TQString</a>& filename )
{
<a href="ntqfile.html">TQFile</a> file( filename );
if ( !file.<a href="ntqfile.html#open">open</a>( <a href="ntqfile.html#open">IO_ReadOnly</a> ) ) {
<a href="ntqmainwindow.html#statusBar">statusBar</a>()->message( TQString( "Failed to load \'%1\'" ).
arg( filename ), 2000 );
return;
}
init(); // Make sure we have colours
m_filename = filename;
<a href="ntqtextstream.html">TQTextStream</a> ts( &file );
Element element;
int errors = 0;
int i = 0;
<a name="x2592"></a> while ( !ts.<a href="ntqtextstream.html#eof">eof</a>() ) {
ts >> element;
if ( element.isValid() )
m_elements[i++] = element;
</pre><pre> <a name="x2590"></a> file.<a href="ntqfile.html#close">close</a>();
</pre>
<p> <pre> <a href="ntqwidget.html#setCaption">setCaption</a>( TQString( "Chart -- %1" ).arg( filename ) );
updateRecentFiles( filename );
drawElements();
m_changed = FALSE;
}
</pre>
<p> Loading a data set is very easy. We open the file and create a text
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.
All the detail is handled by the <tt>Element</tt> class. Then we close
the file and update the caption and the recent files list. Finally we
draw the chart and mark it as unchanged.
<p> <h2> Writing Chart Data
</h2>
<a name="2"></a><p> <pre> void ChartForm::fileSave()
{
</pre><pre> <a href="ntqfile.html">TQFile</a> file( m_filename );
<a name="x2591"></a> if ( !file.<a href="ntqfile.html#open">open</a>( <a href="ntqfile.html#open">IO_WriteOnly</a> ) ) {
<a href="ntqmainwindow.html#statusBar">statusBar</a>()->message( TQString( "Failed to save \'%1\'" ).
arg( m_filename ), 2000 );
return;
}
<a href="ntqtextstream.html">TQTextStream</a> ts( &file );
for ( int i = 0; i < MAX_ELEMENTS; ++i )
if ( m_elements[i].isValid() )
ts << m_elements[i];
file.<a href="ntqfile.html#close">close</a>();
<a href="ntqwidget.html#setCaption">setCaption</a>( TQString( "Chart -- %1" ).arg( m_filename ) );
<a href="ntqmainwindow.html#statusBar">statusBar</a>()->message( TQString( "Saved \'%1\'" ).arg( m_filename ), 2000 );
m_changed = FALSE;
}
</pre>
<p> Saving data is equally easy. We open the file and create a text
stream. We then stream every valid element to the text stream. All the
detail is handled by the <tt>Element</tt> class.
<p> <p align="right">
<a href="tutorial2-06.html">« Canvas Control</a> |
<a href="tutorial2.html">Contents</a> |
<a href="tutorial2-08.html">Taking Data »</a>
</p>
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