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A dispatcher is an instance of the `CollectingDispatcher` class used to generate responses to send back to the user.

## CollectingDispatcher

`CollectingDispatcher` has one method, `utter_message`, and one attribute, `messages`. It is used in an action's `run` method to add responses to the payload returned to the Rasa server. The Rasa server will in turn add `BotUttered` events to the tracker for each response. Responses added using the dispatcher should therefore not be returned explicitly as [events](https://legacy-docs-oss.rasa.com/docs/rasa/action-server/events). For example, the following custom action returns no events explicitly but will return the response, "Hi, User!" to the user:

```python
class ActionGreetUser(Action):
    def name(self) -> Text:
        return "action_greet_user"

async def run(self,
                  dispatcher: CollectingDispatcher,
                  tracker: Tracker,
                  domain: Dict[Text, Any],
                 ) -> List[EventType]:
        dispatcher.utter_message(text="Hi, User!")
        return []
```

### CollectingDispatcher.utter_message

The `utter_message` method can be used to return any type of response to the user.

#### **Parameters**

The `utter_message` method takes the following optional arguments. Passing no arguments will result in an empty message being returned to the user. Passing multiple arguments will result in a rich response (e.g. text and buttons) being returned to the user.

- `text`: The text to return to the user.
  ```python
dispatcher.utter_message(text="Hey there")
```
- `image`: An image URL or file path that will be used to display an image to the user.
  ```python
dispatcher.utter_message(image="https://i.imgur.com/nGF1K8f.jpg")
```
- `json_message`: A custom json payload as a dictionary. It can be used to send [channel specific responses](https://legacy-docs-oss.rasa.com/docs/rasa/responses). The following example would return a date picker in Slack:
  ```python
date_picker = {
    "blocks": [
        {
            "type": "section",
            "text": {
                "text": "Make a bet on when the world will end:",
                "type": "mrkdwn"
            },
            "accessory": {
                "type": "datepicker",
                "initial_date": "2019-05-21",
                "placeholder": {
                    "type": "plain_text",
                    "text": "Select a date"
                }
            }
        }
    ]
}

dispatcher.utter_message(json_message=date_picker)
```
- `response`: The name of a response to return to the user. This response should be specified in your assistant's [domain](https://legacy-docs-oss.rasa.com/docs/rasa/domain).
  ```python
dispatcher.utter_message(response="utter_greet")
```
- `attachment`: A URL or file path of an attachment to return to the user.
  ```python
dispatcher.utter_message(attachment="")
```
- `buttons`: A list of buttons to return to the user. Each button is a dictionary and should have a `title` and a `payload` key. A button can include other keys, but these will only be used if a specific channel looks for them. The button's `payload` will be sent as a user message if the user clicks the button.
  ```python
dispatcher.utter_message(buttons=[
    {"payload": "/affirm", "title": "Yes"},
    {"payload": "/deny", "title": "No"},
])
```
- `elements`: These are specific to using Facebook as a messaging channel. For details of expected format see [Facebook's documentation](https://developers.facebook.com/docs/messenger-platform/send-messages/template/generic/)
- `**kwargs`: arbitrary keyword arguments, which can be used to specify values for [variable interpolation in response variations](https://legacy-docs-oss.rasa.com/docs/rasa/responses). For example, given the following response:
  ```yaml
  responses:
    utter_greet_name:
      - text: Hi {name}!
  ```
  You could specify the name with:
  ```python
dispatcher.utter_message(response="utter_greet_name", name="Aimee")
```

#### **Return type**

`None`