GObjectADD_PRIVATE

A convenience macro to ease adding private data to instances of a new type in the _C_ section of G_DEFINE_TYPE_WITH_CODE() or G_DEFINE_ABSTRACT_TYPE_WITH_CODE().

For instance:

  typedef struct _MyObject MyObject;
  typedef struct _MyObjectClass MyObjectClass;

  typedef struct {
    gint foo;
    gint bar;
  } MyObjectPrivate;

  G_DEFINE_TYPE_WITH_CODE (MyObject, my_object, G_TYPE_OBJECT,
                           G_ADD_PRIVATE (MyObject))

Will add MyObjectPrivate as the private data to any instance of the MyObject type.

G_DEFINE_TYPE_* macros will automatically create a private function based on the arguments to this macro, which can be used to safely retrieve the private data from an instance of the type; for instance:

  gint
  my_object_get_foo (MyObject *obj)
  {
    MyObjectPrivate *priv = my_object_get_instance_private (obj);

    g_return_val_if_fail (MY_IS_OBJECT (obj), 0);

    return priv->foo;
  }

  void
  my_object_set_bar (MyObject *obj,
                     gint      bar)
  {
    MyObjectPrivate *priv = my_object_get_instance_private (obj);

    g_return_if_fail (MY_IS_OBJECT (obj));

    if (priv->bar != bar)
      priv->bar = bar;
  }

Since GLib 2.72, the returned MyObjectPrivate pointer is guaranteed to be aligned to at least the alignment of the largest basic GLib type (typically this is #guint64 or #gdouble). If you need larger alignment for an element in the struct, you should allocate it on the heap (aligned), or arrange for your MyObjectPrivate struct to be appropriately padded.

Note that this macro can only be used together with the G_DEFINE_TYPE_* macros, since it depends on variable names from those macros.

Also note that private structs added with these macros must have a struct name of the form TypeNamePrivate.

It is safe to call the _get_instance_private function on NULL or invalid objects since it’s only adding an offset to the instance pointer. In that case the returned pointer must not be dereferenced.

Available since: 2.38

This function is not directly available to language bindings.