UpdateClass

Modify or extend existing classes dynamically.

Quick Example

import typemap_extensions as tm
from typing import Literal, Callable, Self

type InitFn[T] = tm.Member[
    Literal["__init__"],
    Callable[[tm.Param[Literal["self"], Self], *params], None],
]

class Model:
    def __init_subclass__(cls) -> tm.UpdateClass[InitFn[cls]]:
        super().__init_subclass__()

Signature

class UpdateClass[*Ms]:
    """Update an existing class with new members."""

What It Does

UpdateClass is used with __init_subclass__ to dynamically add or modify members when a class is subclassed.

Usage

Add Methods Dynamically

class MyBase:
    def __init_subclass__(cls, **kwargs) -> tm.UpdateClass[...]:
        # Add a method to each subclass
        cls.describe = lambda self: f"I'm a {cls.__name__}"
        super().__init_subclass__()

class User(MyBase):
    pass

User().describe()  # "I'm a User"

Use Cases

Dataclass-like behavior - Auto-generate __init__, __repr__, etc.
ORM models - Add query methods to models
Plugin systems - Extend classes dynamically

Note: This is an advanced feature. Most users won't need to use UpdateClass directly.