# 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
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.

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

## 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. 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. You can do this by writing a helper validation function with the name `validate_{slot-name}`.

## Handling unhappy paths
The way this works with forms is that a form will raise an `ActionExecutionRejection` if the user didn’t provide the requested information. You need to handle events that might cause `ActionExecutionRejection` errors in your stories.

## The requested_slot slot
The slot `requested_slot` is automatically added to the domain as an unfeaturized slot.

## Handling conditional slot logic
Many forms require more logic than just requesting a list of fields. You can achieve this by writing some logic into the `required_slots()` method:

```
@staticmethod
def required_slots(tracker) -> List[Text]:
   if tracker.get_slot('cuisine') == 'greek':
     return ["cuisine", "num_people", "outdoor_seating", "preferences", "feedback"]
   else:
     return ["cuisine", "num_people", "preferences", "feedback"]
```

## Debugging
The first thing to try is to run your bot with the `--debug` flag. If you are just getting started, you probably only have a few hand-written stories.