Required Fields¶

Set required=True when a value must be present.

Required fields raise Field.RequiredError when:

1. You read field.value before assigning a valid value.
2. You create a Model without providing the required field.
3. You delete a required field from a model.

Default Values¶

Defaults can be static values or factories.

from datetime import UTC, datetime
import uuid

Field(default=0)
Field(default=uuid.uuid4)
Field(default=lambda: datetime.now(UTC))

Defaults are applied when:

1. A standalone Field is created.
2. Field.reset() is called.
3. A Model is created without a value for that field.
4. A model field with a default is deleted.

Use has_default when you need to know whether a default was configured. Field(default=None).has_default is True.

Granted Values¶

Granted values always pass validation, even if later validators would reject them.

field = Field(grant=[None]).instance(str)
field.value = None

Model Field Typing¶

Model field types come from annotations.

from typing import Annotated

from dictify import Field, Model


class User(Model):
    email: Annotated[
        str,
        "primary email",
        Field(required=True).match(r".+@.+"),
    ]
    age: Annotated[int | None, Field(default=None)]

When Field(...) is provided inside Annotated[...], it defines the model field without assigning a class value. Other metadata is ignored for runtime typing.

Direct assignment style remains supported for compatibility:

class User(Model):
    email: str = Field(required=True).match(r".+@.+")

This style is fully supported at runtime. For strict static type checking, prefer Annotated[str, Field(...)]. Do not combine both forms for the same field.