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Once the interface is defined, implementing it is rather trivial.
The first step is to define a normal final GObject class exactly as in the section called “Boilerplate header code”.
The second step is to implement ViewerFile by defining
it using
G_DEFINE_TYPE_WITH_CODE
and
G_IMPLEMENT_INTERFACE
instead of
G_DEFINE_TYPE:
static void viewer_file_editable_interface_init (ViewerEditableInterface *iface);
G_DEFINE_TYPE_WITH_CODE (ViewerFile, viewer_file, G_TYPE_OBJECT,
G_IMPLEMENT_INTERFACE (VIEWER_TYPE_EDITABLE,
viewer_file_editable_interface_init))
This definition is very much like all the similar functions seen
previously. The only interface-specific code present here is the use of
G_IMPLEMENT_INTERFACE.
Classes can implement multiple interfaces by using multiple calls to
G_IMPLEMENT_INTERFACE
inside the call to
G_DEFINE_TYPE_WITH_CODE
viewer_file_editable_interface_init, the interface
initialization function: inside it every virtual method of the interface
must be assigned to its implementation:
static void
viewer_file_editable_save (ViewerFile *self,
GError **error)
{
g_print ("File implementation of editable interface save method: %s.\n",
self->filename);
}
static void
viewer_file_editable_undo (ViewerFile *self,
guint n_steps)
{
g_print ("File implementation of editable interface undo method: %s.\n",
self->filename);
}
static void
viewer_file_editable_redo (ViewerFile *self,
guint n_steps)
{
g_print ("File implementation of editable interface redo method: %s.\n",
self->filename);
}
static void
viewer_file_editable_interface_init (ViewerEditableInterface *iface)
{
iface->save = viewer_file_editable_save;
iface->undo = viewer_file_editable_undo;
iface->redo = viewer_file_editable_redo;
}
static void
viewer_file_init (ViewerFile *self)
{
/* Instance variable initialisation code. */
}