doc/html/tutorial2-07.html


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<title>File Handling</title>
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<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>&amp; 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>()-&gt;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( &amp;file );
        Element element;
        int errors = 0;
        int i = 0;
    <a name="x2592"></a>    while ( !ts.<a href="ntqtextstream.html#eof">eof</a>() ) {
            ts &gt;&gt; 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>()-&gt;message( TQString( "Failed to save \'%1\'" ).
                                    arg( m_filename ), 2000 );
            return;
        }
        <a href="ntqtextstream.html">TQTextStream</a> ts( &amp;file );
        for ( int i = 0; i &lt; MAX_ELEMENTS; ++i )
            if ( m_elements[i].isValid() )
                ts &lt;&lt; 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>()-&gt;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">&laquo; Canvas Control</a> |
<a href="tutorial2.html">Contents</a> |
<a href="tutorial2-08.html">Taking Data &raquo;</a>
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