how to define custom transmute?

[xbanke]

• typical version: 2.0.15
• Python version: 3.7.4
• Operating System: Centos

Description

Hey, @seandstewart . There's some cases which user want to define custom transmute:

import json
import typic
from typing import Any

@typic.klass
class Foo:
    a: int
    b: str
    
    @classmethod
    def transmute(cls, v: Any) -> 'Foo':
        if isinstance(v, str):
            try:
                v = json.loads(v)
            except:
                pass
        if isinstance(v, str):
            v = v.split(',')
        if isinstance(v, list):
            return cls(*v)
        return typic.transmute(cls, v)

Expect:

Foo.transmute('1,abc')
# >>> Foo(a=1, b='abc')

However, after decorated by typic.klass, transmute is replaced.

What I Did

Currently, I have to define a metaclass as following:

import json
import typic
from typing import Any, Dict, Tuple, Type
from types import MethodType

class FooMeta(type):
    def __new__(mcs, name: str, bases: Tuple[Type, ...], namespace: Dict[str, Any]):
        cls = type.__new__(mcs, name, bases, namespace)
        transmute = getattr(cls, 'transmute', None)
        cls = typic.klass(cls)
        if isinstance(transmute, MethodType):
            setattr(cls, 'transmute', transmute)
            typic.register(transmute, lambda a: a is cls)
        return cls

    
class Foo(metaclass=FooMeta):
    a: int
    b: str
    
    @classmethod
    def transmute(cls, v: Any) -> 'Foo':
        if isinstance(v, str):
            try:
                v = json.loads(v)
            except:
                pass
        if isinstance(v, str):
            v = v.split(',')
        if isinstance(v, list):
            return cls(*v)
        return typic.transmute(cls, v)

@typic.al
def foo(f: Foo):
    print(f)

foo('1,abc')  # Foo(a=1, b='abc')

But, there's some error with pycharm type hinting.

[seandstewart]

Thanks for raising this issue, this relates to the work described in #56. I'll take this approach under consideration when I re-define the API for registering custom Ser/Des protocols!