Skip a method when an instance attribute is missing or None.
Parameters:
-
variable_name
(str)
–
Name of the instance attribute to require.
Returns:
-
Callable
–
A decorator. The wrapped method returns None when the attribute is
-
Callable
–
Examples:
>>> from ures.tools.decorator import check_instance_variable
>>> class Worker:
... def __init__(self):
... self.client = None
... @check_instance_variable("client")
... def ping(self):
... return "ok"
>>> Worker().ping() is None
True
Source code in ures/tools/decorator.py
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61 | def check_instance_variable(variable_name: str) -> Callable:
"""Skip a method when an instance attribute is missing or ``None``.
Args:
variable_name (str): Name of the instance attribute to require.
Returns:
A decorator. The wrapped method returns None when the attribute is
missing or None.
Examples:
>>> from ures.tools.decorator import check_instance_variable
>>> class Worker:
... def __init__(self):
... self.client = None
... @check_instance_variable("client")
... def ping(self):
... return "ok"
>>> Worker().ping() is None
True
"""
def decorator(method):
@wraps(method)
def wrapper(self, *args, **kwargs):
try:
# Use hasattr to check if the instance has the attribute, and then getattr to get it
if (
hasattr(self, variable_name)
and getattr(self, variable_name) is None
):
# Option 1: Return None
return None
# Option 2: Raise an exception (recommended)
# raise ValueError(f"Instance variable '{variable_name}' cannot be None.")
elif not hasattr(
self, variable_name
): # Handle the case where the attribute doesn't exist at all
raise AttributeError(
f"Instance variable '{variable_name}' does not exist."
)
except (ValueError, AttributeError) as e: # Catch both exceptions
logger.error(f"Error in check_instance_variable decorator: {e}")
return None # Or re-raise the exception: raise
return method(self, *args, **kwargs)
return wrapper
return decorator
|