# lv_obj_class.h (/api/public/core/lv_obj_class_h)
Functions [#functions]
lv_obj_set_external_data [#lv_obj_set_external_data]
Associates an array of external data pointers with an LVGL object.
Associates custom user data with an LVGL object and specifies a destructor function that will be automatically invoked when the object is deleted to properly clean up the associated resources.
```c title=" " lineNumbers=1
void lv_obj_set_external_data(lv_obj_t *obj, void *data, void(*free_cb)(void *data))
```
Parameters
| Name | Type | Description |
| --------- | ------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `obj` | | Target LVGL object |
| `data` | `void *` | User-defined data pointer to associate with a object **May** be `NULL`. |
| `free_cb` | `void(*)(void *data)` | Cleanup function called for each non-NULL data pointer during object deletion. Receives single data pointer as parameter. **May** be `NULL`. When NULL no automatic cleanup is performed. |
lv_obj_class_create_obj [#lv_obj_class_create_obj]
Create an object form a class descriptor
```c title=" " lineNumbers=1
lv_obj_t * lv_obj_class_create_obj(const lv_obj_class_t *class_p, lv_obj_t *parent)
```
Parameters
| Name | Type | Description |
| --------- | ------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------- |
| `class_p` | | pointer to a class |
| `parent` | | pointer to a parent widget **May** be `NULL`.. When NULL, the widget is created as a screen on the default display. |
**Returns:** — pointer to the created object
lv_obj_class_init_obj [#lv_obj_class_init_obj]
```c title=" " lineNumbers=1
void lv_obj_class_init_obj(lv_obj_t *obj)
```
Parameters
| Name | Type |
| ----- | ------------------------------------------------ |
| `obj` | |
lv_obj_is_editable [#lv_obj_is_editable]
```c title=" " lineNumbers=1
bool lv_obj_is_editable(const lv_obj_t *obj)
```
Parameters
| Name | Type |
| ----- | ------------------------------------------------------ |
| `obj` | |
lv_obj_is_group_def [#lv_obj_is_group_def]
```c title=" " lineNumbers=1
bool lv_obj_is_group_def(const lv_obj_t *obj)
```
Parameters
| Name | Type |
| ----- | ------------------------------------------------------ |
| `obj` | |
Enums [#enums]
lv_obj_class_editable_t [#lv_obj_class_editable_t]
| Name | Description |
| ------------------------------- | ----------------------------------------------------------------------------- |
| `LV_OBJ_CLASS_EDITABLE_INHERIT` | Check the base class. Must have 0 value to let zero initialized class inherit |
| `LV_OBJ_CLASS_EDITABLE_TRUE` | |
| `LV_OBJ_CLASS_EDITABLE_FALSE` | |
lv_obj_class_group_def_t [#lv_obj_class_group_def_t]
| Name | Description |
| -------------------------------- | ----------------------------------------------------------------------------- |
| `LV_OBJ_CLASS_GROUP_DEF_INHERIT` | Check the base class. Must have 0 value to let zero initialized class inherit |
| `LV_OBJ_CLASS_GROUP_DEF_TRUE` | |
| `LV_OBJ_CLASS_GROUP_DEF_FALSE` | |
lv_obj_class_theme_inheritable_t [#lv_obj_class_theme_inheritable_t]
| Name | Description |
| -------------------------------------- | ------------------------------------- |
| `LV_OBJ_CLASS_THEME_INHERITABLE_FALSE` | Do not inherit theme from base class. |
| `LV_OBJ_CLASS_THEME_INHERITABLE_TRUE` | |
Typedefs [#typedefs]
lv_obj_class_event_cb_t [#lv_obj_class_event_cb_t]
```c title=" " lineNumbers=1
typedef void(* lv_obj_class_event_cb_t) (lv_obj_class_t *class_p, lv_event_t *e)
```
Dependencies [#dependencies]