# Fields

## Fields

Vibora has a special class called "Field" to represent each field of a schema. You can build any kind of validation rules using this class but to avoid repeat yourself there a few builtin ones. There are a few must-know attributes of this class:

1\) **required** -> By default all declared fields in a schema are required which means they must be present in the validation values. If you have optional fields you must explicitely declare this as `Field(required=False)`

2\) **load\_from** -> Sometimes is useful to deal with friendly names inside a schema but to ofuscate them outside outside your app, by using the `load_from` parameter you can specify where to load this field from or even load two different fields from the same key.

3\) **default** -> A default value in case the key is missing or the value is null.

4\) **validators** -> A list of functions to validate the current value against. This functions can be async or sync and receive one up to two parameters. In case it receives a single parameter then Vibora will pass only the current value to it. In case it receive two parameters the context of the schema will be also provided. The exception `ValidationError` must be raised to notify the schema that this field is invalid, returning values are ignored.

## StringField

Validates if the given value is a valid string.

```python
import uuid
from vibora.schemas import Schema, fields
from vibora.schemas.validators import Length

class NewUserSchema(Schema):

    name: str = fields.String(
        required=False,
        validators=[Length(min=3, max=30)],
        default=lambda: str(uuid.uuid4()),
        strict=False
    )
```

> There is a special attribute called `strict` to allow this field to cast integers and similar types to a string instead of raising an error.


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