| Server IP : 182.53.201.61 / Your IP : 216.73.217.175 Web Server : Apache/2.2.15 (Fedora) System : Linux km10.dyndns.org 2.6.31.5-127.fc12.i686.PAE #1 SMP Sat Nov 7 21:25:57 EST 2009 i686 User : apache ( 48) PHP Version : 5.3.3 Disable Function : NONE MySQL : ON | cURL : ON | WGET : ON | Perl : ON | Python : ON | Sudo : ON | Pkexec : ON Directory : /usr/share/gtk-doc/html/gobject/ |
Upload File : |
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Interface Properties</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
<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="ch06s03.html" title="Interface definition prerequisites">
<link rel="next" href="howto-signals.html" title="How to create and use signals">
<meta name="generator" content="GTK-Doc V1.11 (XML mode)">
<link rel="stylesheet" href="style.css" type="text/css">
<link rel="preface" href="pr01.html" title="Introduction">
<link rel="part" href="pt01.html" title="Part I. Concepts">
<link rel="chapter" href="chapter-intro.html" title="Background">
<link rel="chapter" href="chapter-gtype.html" title="The GLib Dynamic Type System">
<link rel="chapter" href="chapter-gobject.html" title="The GObject base class">
<link rel="chapter" href="chapter-signal.html" title="The GObject messaging system">
<link rel="reference" href="rn01.html" title="API Reference">
<link rel="reference" href="rn02.html" title="Tools Reference">
<link rel="part" href="pt02.html" title="Part IV. Tutorial">
<link rel="chapter" href="howto-gobject.html" title="How to define and implement a new GObject">
<link rel="chapter" href="howto-interface.html" title="How to define and implement interfaces">
<link rel="chapter" href="howto-signals.html" title="How to create and use signals">
<link rel="part" href="pt03.html" title="Part V. Related Tools">
<link rel="chapter" href="tools-vala.html" title="Vala">
<link rel="chapter" href="tools-gob.html" title="GObject builder">
<link rel="chapter" href="tools-ginspector.html" title="Graphical inspection of GObjects">
<link rel="chapter" href="tools-refdb.html" title="Debugging reference count problems">
<link rel="chapter" href="tools-gtkdoc.html" title="Writing API docs">
<link rel="index" href="ix01.html" title="Index">
<link rel="index" href="ix02.html" title="Index of deprecated symbols">
<link rel="index" href="ix03.html" title="Index of new symbols in 2.2">
<link rel="index" href="ix04.html" title="Index of new symbols in 2.4">
<link rel="index" href="ix05.html" title="Index of new symbols in 2.6">
<link rel="index" href="ix06.html" title="Index of new symbols in 2.8">
<link rel="index" href="ix07.html" title="Index of new symbols in 2.10">
<link rel="index" href="ix08.html" title="Index of new symbols in 2.12">
<link rel="index" href="ix09.html" title="Index of new symbols in 2.14">
<link rel="index" href="ix10.html" title="Index of new symbols in 2.18">
<link rel="index" href="ix11.html" title="Index of new symbols in 2.22">
</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="2"><tr valign="middle">
<td><a accesskey="p" href="ch06s03.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td>
<td><a accesskey="u" href="howto-interface.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td>
<th width="100%" align="center">GObject Reference Manual</th>
<td><a accesskey="n" href="howto-signals.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td>
</tr></table>
<div class="sect1" title="Interface Properties">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="howto-interface-properties"></a>Interface Properties</h2></div></div></div>
<p>
Starting from version 2.4 of GLib, GObject interfaces can also have
properties. Declaration of the interface properties is similar to
declaring the properties of ordinary GObject types as explained in
<a class="xref" href="gobject-properties.html" title="Object properties">the section called “Object properties”</a>,
except that <code class="function"><a class="link" href="gobject-The-Base-Object-Type.html#g-object-interface-install-property" title="g_object_interface_install_property ()">g_object_interface_install_property</a></code> is used to
declare the properties instead of <code class="function"><a class="link" href="gobject-The-Base-Object-Type.html#g-object-class-install-property" title="g_object_class_install_property ()">g_object_class_install_property</a></code>.
</p>
<p>
To include a property named 'name' of type <span class="type">string</span> in the
<span class="type">maman_ibaz</span> interface example code above, we only need to
add one
<sup>[<a name="id713500" href="#ftn.id713500" class="footnote">12</a>]</sup>
line in the <code class="function">maman_ibaz_base_init</code>
<sup>[<a name="id713513" href="#ftn.id713513" class="footnote">13</a>]</sup>
as shown below:
</p>
<pre class="programlisting">
static void
maman_ibaz_base_init (gpointer g_iface)
{
static gboolean is_initialized = FALSE;
if (!is_initialized)
{
g_object_interface_install_property (g_iface,
g_param_spec_string ("name",
"Name",
"Name of the MamanIbaz",
"maman",
G_PARAM_READWRITE));
is_initialized = TRUE;
}
}
</pre>
<p>
</p>
<p>
One point worth noting is that the declared property wasn't assigned an
integer ID. The reason being that integer IDs of properties are used
only inside the get and set methods and since interfaces do not
implement properties, there is no need to assign integer IDs to
interface properties.
</p>
<p>
An implementation shall declare and define it's properties in the usual
way as explained in <a class="xref" href="gobject-properties.html" title="Object properties">the section called “Object properties”</a>, except for one
small change: it must declare the properties of the interface it
implements using <code class="function"><a class="link" href="gobject-The-Base-Object-Type.html#g-object-class-override-property" title="g_object_class_override_property ()">g_object_class_override_property</a></code>
instead of <code class="function"><a class="link" href="gobject-The-Base-Object-Type.html#g-object-class-install-property" title="g_object_class_install_property ()">g_object_class_install_property</a></code>.
The following code snippet shows the modifications needed in the
<span class="type">MamanBaz</span> declaration and implementation above:
</p>
<pre class="programlisting">
struct _MamanBaz
{
GObject parent_instance;
gint instance_member;
gchar *name;
};
enum
{
PROP_0,
PROP_NAME
};
static void
maman_baz_set_property (GObject *object,
guint property_id,
const GValue *value,
GParamSpec *pspec)
{
MamanBaz *baz = MAMAN_BAZ (object);
GObject *obj;
switch (prop_id)
{
case ARG_NAME:
g_free (baz->name);
baz->name = g_value_dup_string (value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
maman_baz_get_property (GObject *object,
guint prop_id,
GValue *value,
GParamSpec *pspec)
{
MamanBaz *baz = MAMAN_BAZ (object);
switch (prop_id)
{
case ARG_NAME:
g_value_set_string (value, baz->name);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
maman_baz_class_init (MamanBazClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
gobject_class->set_property = maman_baz_set_property;
gobject_class->get_property = maman_baz_get_property;
g_object_class_override_property (gobject_class, PROP_NAME, "name");
}
</pre>
<p>
</p>
<div class="footnotes">
<br><hr width="100" align="left">
<div class="footnote"><p><sup>[<a name="ftn.id713500" href="#id713500" class="para">12</a>] </sup>
That really is one line extended to six for the sake of clarity
</p></div>
<div class="footnote"><p><sup>[<a name="ftn.id713513" href="#id713513" class="para">13</a>] </sup>
The <code class="function"><a class="link" href="gobject-The-Base-Object-Type.html#g-object-interface-install-property" title="g_object_interface_install_property ()">g_object_interface_install_property</a></code>
can also be called from <code class="function">class_init</code> but it must
not be called after that point.
</p></div>
</div>
</div>
<div class="footer">
<hr>
Generated by GTK-Doc V1.11</div>
</body>
</html>