# ClassesMapping
## Introduction
**`Classes Mapping`** widget allows to rename given object classes with new names. It can be useful when you want to rename classes in your project.
## Function signature
```python
classes_mapping = ClassesMapping(
classes=obj_classes,
empty_notification=None,
widget_id=None
)
```
{% tabs %}
{% tab title="Default with classes" %}
Default with classes
{% endtab %}
{% tab title="Default without classes" %}
Default without classes
{% endtab %}
{% endtabs %}
## Parameters
| Parameters | Type | Description |
| :------------------: | :-----------------------------------------: | :---------------------------------------------------------------------: |
| `classes` | `Union[List[ObjClass], ObjClassCollection]` | Supervisely object class collection or list of object classes |
| `empty_notification` | `NotificationBox` | Notification that will be displayed when there are no classes in widget |
| `widget_id` | `str` | ID of the widget |
### classes
List of `ObjClass` objects or Supervisely object class collection (`ObjClassCollection`).
**type:** `Union[List[ObjClass], ObjClassCollection]`
```python
classes_mapping = ClassesMapping(
classes=obj_classes
)
```
### empty\_notification
Notification that will be displayed when there are no classes in the widget.
**type:** `NotificationBox`
**default** `None`
```python
empty_notificaiton = NotificationBox(
title="No classes", description="Provide classes to widget in order to map new names."
)
classes_mapping = ClassesMapping(
classes=obj_classes,
empty_notification=empty_notificaiton
)
```
### widget\_id
ID of the widget.
**type:** `str`
**default value:** `None`
## Methods and attributes
| Attributes and Methods | Description |
| :--------------------: | --------------------------------------------------------- |
| `set()` | Set classes to widget. |
| `get_classes()` | Return list of all classes. |
| `get_mapping()` | Return edited classes mapping, if there were any changes. |
| `ignore()` | Ignore classes by indexes. |
| `set_default()` | Revert changes. |
| `set_mapping()` | Set new classes mapping. |
| `select_all()` | Select all classes. |
| `deselect_all()` | Deselect all classes. |
| `select()` | Select classes by `ObjClass`. |
| `@selection_changed` | Callback triggers when selection is changed. |
## Mini App Example
You can find this example in our Github repository:
[supervisely-ecosystem/ui-widgets-demos/input/009\_classes\_mapping/src/main.py](https://github.com/supervisely-ecosystem/ui-widgets-demos/blob/master/input/009_classes_mapping/src/main.py)
### Import libraries
```python
import os
import supervisely as sly
from supervisely.app.widgets import Card, Container, ClassesMapping, Button, Text, NotificationBox
from dotenv import load_dotenv
```
### Init API client
First, we load environment variables with credentials and init API for communicating with Supervisely Instance:
```python
load_dotenv("local.env")
load_dotenv(os.path.expanduser("~/supervisely.env"))
api = sly.Api()
```
### Create list of object classes
```python
cat_obj_class = sly.ObjClass("cat", sly.Rectangle)
dog_obj_class = sly.ObjClass("dog", sly.Polygon)
horse_obj_class = sly.ObjClass("horse", sly.Bitmap)
cow_obj_class = sly.ObjClass("cow", sly.Polyline)
zebra_obj_class = sly.ObjClass("zebra", sly.Point)
obj_classes = [
cat_obj_class,
dog_obj_class,
horse_obj_class,
cow_obj_class,
zebra_obj_class,
]
```
### Initialize `ClassesMapping` widget, `NotificationBox` widget for custom notification
```python
empty_notification = NotificationBox(
title="No classes", description="Provide classes to widget in order to map new names."
)
classes_mapping = ClassesMapping(
classes=obj_classes,
empty_notification=empty_notification
)
```
### Create `Text` widget for displaying changes and `Button` widget for saving changes
```python
new_classes_names = Text(f"Press button to save changes", "info")
save_button = Button("Save", button_size="mini")
```
### Create app layout
Prepare a layout for the app using the `Card` widget with the `content` parameter and place the widget that we've just created into the `Container` widget.
```python
container = Container([classes_mapping, new_classes_names, save_button])
card = Card(
title="Classes Mapping",
content=container,
)
layout = Container(widgets=[card])
```
### Create the app using the layout
Create an app object with the layout parameter.
```python
app = sly.Application(layout=layout)
```
### Add functions to control widgets from the python code
```python
@save_button.click
def save_mapping():
new_classes_names.hide()
mapping = classes_mapping.get_mapping()
new_class_names = []
for obj_class in obj_classes:
if obj_class.name in mapping:
new_class_name = mapping[obj_class.name]["value"]
if new_class_name != obj_class.name:
new_class_names.append(new_class_name)
if len(new_class_names) == 0:
new_classes_names.set(f"No changes detected", "info")
else:
new_classes_names.set(f"New classes names: {','.join(new_class_names)}", "success")
new_classes_names.show()
```
