argguard

ArgGuard

ArgGuard is a simple abstract utility class to remove some boilerplate code when asserting class arguments.

Usage

The ArgGuard class provides the protected abstract _argGuard method. This is the method where all assertions, checks and validations of the class arguments should take place. Every class that extends the ArgGuard class needs to implement this method.

A second central method is _assert_args which stores the provided arguments and calls _argGuard. This method should be called as soon as possible in the constructor of the class to be guarded.

API

Method	Args	Description
_arg_guard	self	Abstract method where all assertions should take pace
_assert_args	self, args	Stores the provided arguments and calls _argGuard
_get_args	self, *requested_args	Retrieves all requested arguments
_get_required_args	self, *requested_args	Retrieves all requested arguments and fails if they are missing

Example

# Without ArgGuard
class A:
    def __init__(self, a, b, c=0):
        assert (
            'a' in self.__args
        ), 'Required argument "a" is missing'

        assert (
            'b' in self.__args
        ), 'Required argument "b" is missing'

        assert (
            a % b == 0
        ), 'a ({}) must be divisible by b ({})'.format(a, b)

        self.state = a // b + c

# With ArgGuard
class A(ArgGuard):
    def __init__(self, a, b, c=0):
        self._assert_args(locals())
        self.state = a // b + c

    def _arg_guard(self):
        # If a required argument is missing, an error is thrown
        a, b = self._get_required_args('a', 'b')

        assert (
            a % b == 0
        ), 'a ({}) must be divisible by b ({})'.format(a, b)