Using Callbacks & Rules

Using rules with Callback:

Example:

from kwhelp import KwargsHelper, AfterAssignEventArgs, BeforeAssignEventArgs, AssignBuilder
import kwhelp.rules as rules

class MyClass:
    def __init__(self, **kwargs):
        self._loop_count = -1
        kw = KwargsHelper(self, {**kwargs})
        ab = AssignBuilder()
        kw.add_handler_before_assign(self._arg_before_cb)
        kw.add_handler_after_assign(self._arg_after_cb)
        ab.append(key='exporter', rules=[rules.RuleStr])
        ab.append(key='name', require=True, rules=[rules.RuleStr],
                default='unknown')
        ab.append(key='file_name', require=True, rules_all=[
            rules.RuleStr, rules.RuleStrNotNullOrEmpty])
        ab.append(key='loop_count', require=True, rules_all=[
                rules.RuleInt, rules.RuleIntPositive],
                default=self._loop_count)
        result = True
        # by default assign will raise errors if conditions are not met.
        for arg in ab:
            result = kw.assign_helper(arg)
            if result == False:
                break
        if result == False:
            raise ValueError("Error parsing kwargs")

    def _arg_before_cb(self, helper: KwargsHelper,
                    args: BeforeAssignEventArgs) -> None:
        if args.key == 'name' and args.field_value == 'unknown':
            args.field_value = 'None'

    def _arg_after_cb(self, helper: KwargsHelper,
                    args: AfterAssignEventArgs) -> None:
        # callback function after value assigned to attribute
        if args.key == 'name' and args.field_value == 'unknown':
            raise ValueError(
                f"{args.key} This should never happen. value was suppose to be reassigned")

    @property
    def exporter(self) -> str:
        return self._exporter

    @property
    def file_name(self) -> str:
        return self._file_name

    @property
    def name(self) -> str:
        return self._name

    @property
    def loop_count(self) -> int:
        return self._loop_count

>>> my_class = MyClass(exporter='json', file_name='data.json', loop_count=3)
>>> print(my_class.exporter)
json
>>> print(my_class.file_name)
data.json
>>> print(my_class.name)
None
>>> print(my_class.loop_count)
3