# Forms

Note  
There is an in-depth tutorial [here](https://blog.rasa.com/building-contextual-assistants-with-rasa-formaction/) about how to use Rasa Forms for slot filling.

- [Configuration File](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#configuration-file)
- [Form Basics](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#form-basics)
- [Custom slot mappings](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#custom-slot-mappings)
- [Validating user input](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#validating-user-input)
- [Handling unhappy paths](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#handling-unhappy-paths)
- [The requested_slot slot](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#the-requested-slot-slot)
- [Handling conditional slot logic](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#handling-conditional-slot-logic)
- [Debugging](https://legacy-docs-v1.rasa.com/1.10.19/core/forms/#debugging)

## Overview of Form Actions
One of the most common conversation patterns is to collect a few pieces of information from a user in order to do something (book a restaurant, call an API, search a database, etc.). This is also called **slot filling**.

If you need to collect multiple pieces of information in a row, we recommended that you create a `FormAction`. This is a single action which contains the logic to loop over the required slots and ask the user for this information. There is a full example using forms in the `examples/formbot` directory of Rasa Core.

### Defining a Form
When you define a form, you need to add it to your domain file.
If your form’s name is `restaurant_form`, your domain would look like this:

```
forms:
  - restaurant_form
actions:
  ...
```

### Configuration File
To use forms, you also need to include the `FormPolicy` in your policy configuration file. For example:

```
policies:
  - name: "FormPolicy"
```

### Form Basics
Using a `FormAction`, you can describe _all_ of the happy paths with a single story. By “happy path”, we mean that whenever you ask a user for some information, they respond with the information you asked for.

If we take the example of the restaurant bot, this single story describes all of the happy paths.

```
## happy path
* request_restaurant
    - restaurant_form
    - form{"name": "restaurant_form"}
    - form{"name": null}
```

In this story the user intent is `request_restaurant`, which is followed by the form action `restaurant_form`. With `form{"name": "restaurant_form"}` the form is activated and with `form{"name": null}` the form is deactivated again.

The `FormAction` will only request slots which haven’t already been set.
If a user starts the conversation with
I’d like a vegetarian Chinese restaurant for 8 people, then they won’t be asked about the `cuisine` and `num_people` slots.

## Custom Slot Mappings
If you do not define slot mappings, slots will be only filled by entities with the same name as the slot that are picked up from the user input.

### Example for the Restaurant Bot
Here’s an example for the restaurant bot:

```
def slot_mappings(self) -> Dict[Text, Union[Dict, List[Dict]]]:
    return {
        "cuisine": self.from_entity(entity="cuisine", not_intent="chitchat"),
        "num_people": [
            self.from_entity(
                entity="number", intent=["inform", "request_restaurant"]
            ),
        ],
        "outdoor_seating": [
            self.from_entity(entity="seating"),
            self.from_intent(intent="affirm", value=True),
            self.from_intent(intent="deny", value=False),
        ],
        "preferences": [
            self.from_intent(intent="deny", value="no additional preferences"),
            self.from_text(not_intent="affirm"),
        ],
        "feedback": [self.from_entity(entity="feedback"), self.from_text()],
    }
```

## Validating User Input
After extracting a slot value from user input, the form will try to validate the value of the slot.

```python
def validate_cuisine(
    self,
    value: Text,
    dispatcher: CollectingDispatcher,
    tracker: Tracker,
    domain: Dict[Text, Any],
) -> Dict[Text, Any]:
    if value.lower() in self.cuisine_db():
        return {"cuisine": value}
    else:
        dispatcher.utter_message(template="utter_wrong_cuisine")
        return {"cuisine": None}
```

The helper validation functions return dictionaries of slot names and values to set.

## Handling Unhappy Paths
Of course your users will not always respond with the information you ask of them. Typically, users will ask questions, make chitchat, change their mind, or otherwise stray from the happy path. The way this works with forms is that a form will raise an `ActionExecutionRejection` if the user didn’t provide the requested information.

Use [Interactive Learning with Forms](https://legacy-docs-v1.rasa.com/1.10.19/core/interactive-learning/#section-interactive-learning-forms) to build these stories effectively.

## Debugging
The first thing to try is to run your bot with the `--debug` flag, see [Command Line Interface](https://legacy-docs-v1.rasa.com/1.10.19/user-guide/command-line-interface/#command-line-interface) for details.