Validators

Validators are a vital part of any data validation library. Oblate, apart from providing built-in validation features, also provides the ability of writing custom validators.

This is done using the validate.field() function:

class User(oblate.Schema):
    id = fields.Integer()
    username = fields.String()
    is_employee = fields.Boolean(default=False)

    @validate.field(id)
    def validate_id_range(self, value, ctx):
        assert value >= 1000 and value <= 9999, 'Value must be in range 1000-9999 inclusive'

Initializing the schema with invalid data:

User({'id': 340})

causes the following error:

oblate.exceptions.ValidationError:
│
│ 2 validation errors in schema 'User'
│
└── In field id:
    └── Value must be in range 1000-9999 inclusive
│
└── In field username:
    └── This field is required.