Via typecasts

We will continue to use the Spell class described in the previous chapter.

The default internal type for SQS has str as its internal type. That means SQSSender[Spell] must know how to convert Spell to str, and SQSReceiver[Spell] must know how to convert str back to Spell.

import operator
from typecasts import casts
from platonic.sqs.queue import SQSSender

class Spell:
    """Magical spell."""

    def __init__(self, text: str) -> None:
        self.text = text

casts[Spell, str] = operator.attrgetter('text')
casts[str, Spell] = Spell


Very simple, as you can see. Once you have declared the necessary casts, all Platonic data structures will know how to use your custom classes.

Of course, in many cases you don't even need to do that because built-in classes or Pydantic models you're using are supported by typecasts by default.