Field validators as schema methods?

Often, validators and preprocessors only apply to a single Schema, so it may make sense to define them within the Schema–rather than as separate functions–for better cohesion.

Method names could be passed to __validators__, et. al, like so:

class UserSchema(Schema):
    __validators__ = ['validate_schema']

    def validate_schema(self, data):
        # ...

[philtay]

@sloria What about something like this?

class User(Schema):
    name = fields.String()
    age = fields.Integer()

    @validator('age')
    def ensure_adult(self, value):
        if value < 18:
            raise ValidationError('Too young!')

It would be a nice convenience.

[taion]

Awesome! Sorry I didn’t get around to coding this up. Thanks!