Default page

Your IP: 216.73.216.10
Server IP: 157.245.101.34
Server: Linux skvinfotech-website 5.4.0-131-generic #147-Ubuntu SMP Fri Oct 14 17:07:22 UTC 2022 x86_64
Server Software: Apache/2.4.41 (Ubuntu)
PHP Version: 7.4.33
Buat File | Buat Folder

Dir : ~/usr/share/doc/libglib2.0-doc/gobject/

Edit File: howto-interface-override.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Overriding interface methods: GObject Reference Manual</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
<link rel="home" href="index.html" title="GObject Reference Manual">
<link rel="up" href="howto-interface.html" title="How to define and implement interfaces">
<link rel="prev" href="howto-interface-properties.html" title="Interface properties">
<link rel="next" href="howto-signals.html" title="How to create and use signals">
<meta name="generator" content="GTK-Doc V1.32 (XML mode)">
<link rel="stylesheet" href="style.css" type="text/css">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle">
<td width="100%" align="left" class="shortcuts"></td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td>
<td><a accesskey="u" href="howto-interface.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td>
<td><a accesskey="p" href="howto-interface-properties.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td>
<td><a accesskey="n" href="howto-signals.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td>
</tr></table>
<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="howto-interface-override"></a>Overriding interface methods</h2></div></div></div>

 If a base class already implements an interface and a derived
 class needs to implement the same interface but needs to override certain
 methods, you must reimplement the interface and set only the interface
 methods which need overriding.
 

 In this example, ViewerAudioFile is derived from
 ViewerFile. Both implement the ViewerEditable
 interface. ViewerAudioFile only implements one method of the
 ViewerEditable interface and uses the base class implementation of
 the other.

<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36</pre></td>
 <td class="listing_code"><pre class="programlisting">static void
viewer_audio_file_editable_save (ViewerEditable *editable,
 GError **error)
{
 ViewerAudioFile *self = VIEWER_AUDIO_FILE (editable);

g_print ("Audio file implementation of editable interface save method.\n");
}

static void
viewer_audio_file_editable_interface_init (ViewerEditableInterface *iface)
{
 /* Override the implementation of save(). */
 iface->save = viewer_audio_file_editable_save;

/*
 * Leave iface->undo and ->redo alone, they are already set to the
 * base class implementation.
 */
}

G_DEFINE_TYPE_WITH_CODE (ViewerAudioFile, viewer_audio_file, VIEWER_TYPE_FILE,
 G_IMPLEMENT_INTERFACE (VIEWER_TYPE_EDITABLE,
 viewer_audio_file_editable_interface_init))

static void
viewer_audio_file_class_init (ViewerAudioFileClass *klass)
{
 /* Nothing here. */
}

static void
viewer_audio_file_init (ViewerAudioFile *self)
{
 /* Nothing here. */
}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

To access the base class interface implementation use
 <code class="function"><a class="link" href="gobject-Type-Information.html#g-type-interface-peek-parent" title="g_type_interface_peek_parent ()">g_type_interface_peek_parent</a></code>
 from within an interface's <code class="function">default_init</code> function.
 

 To call the base class implementation of an interface
 method from a derived class where than interface method has been
 overridden, stash away the pointer returned from
 <code class="function"><a class="link" href="gobject-Type-Information.html#g-type-interface-peek-parent" title="g_type_interface_peek_parent ()">g_type_interface_peek_parent</a></code>
 in a global variable.
 

 In this example ViewerAudioFile overrides the
 <code class="function">save</code> interface method. In its overridden method
 it calls the base class implementation of the same interface method.

<div class="informalexample">
 <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
 <tbody>
 <tr>
 <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37</pre></td>
 <td class="listing_code"><pre class="programlisting">static ViewerEditableInterface *viewer_editable_parent_interface = NULL;

static void
viewer_audio_file_editable_save (ViewerEditable *editable,
 GError **error)
{
 ViewerAudioFile *self = VIEWER_AUDIO_FILE (editable);

g_print ("Audio file implementation of editable interface save method.\n");

/* Now call the base implementation */
 viewer_editable_parent_interface->save (editable, error);
}

static void
viewer_audio_file_editable_interface_init (ViewerEditableInterface *iface)
{
 viewer_editable_parent_interface = g_type_interface_peek_parent (iface);

iface->save = viewer_audio_file_editable_save;
}

G_DEFINE_TYPE_WITH_CODE (ViewerAudioFile, viewer_audio_file, VIEWER_TYPE_FILE,
 G_IMPLEMENT_INTERFACE (VIEWER_TYPE_EDITABLE,
 viewer_audio_file_editable_interface_init))

static void
viewer_audio_file_class_init (ViewerAudioFileClass *klass)
{
 /* Nothing here. */
}

static void
viewer_audio_file_init (ViewerAudioFile *self)
{
 /* Nothing here. */
}</pre></td>
 </tr>
 </tbody>
 </table>
</div>

</div>
<div class="footer">
<hr>Generated by GTK-Doc V1.32</div>
</body>
</html>