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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:
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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:
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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. */ } |
If the object is not of final type, e.g. was declared using
G_DECLARE_DERIVABLE_TYPE
then
G_ADD_PRIVATE
macro should be added. The private structure should be declared exactly
as for a normal derivable object, see the section called “Boilerplate code”.
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G_DEFINE_TYPE_WITH_CODE (ViewerFile, viewer_file, G_TYPE_OBJECT, G_ADD_PRIVATE (ViewerFile) G_IMPLEMENT_INTERFACE (VIEWER_TYPE_EDITABLE, viewer_file_editable_interface_init)) |