Dp Chain Responsibility
DodaTech
1 min read
In this tutorial, you'll learn about How to Fix Chain of Responsibility Errors. We cover key concepts, practical examples, and best practices.
Fix chain of responsibility errors when request processing hardcoded in if/elif chain.
Quick Fix
Wrong
def handle(req):
if 'auth' in req:
print('Auth')
if 'valid' in req:
print('Validate')
if 'log' in req:
print('Log')
else: print('No log')
else: print('Invalid')
else: print('No auth')
Nested conditionals. Adding new handler requires modifying existing code.
Right
from abc import ABC,abstractmethod
class Handler(ABC):
def __init__(self): self.next=None
def set_next(self,h): self.next=h; return h
def handle(self,req):
if self.next: return self.next.handle(req)
return None
class AuthHandler(Handler):
def handle(self,req):
if 'auth' in req: return self.next.handle(req) if self.next else None
return 'No auth'
class ValidateHandler(Handler):
def handle(self,req):
if 'valid' in req: return self.next.handle(req) if self.next else None
return 'Invalid'
class LogHandler(Handler):
def handle(self,req): print('Log'); return None
auth=AuthHandler(); auth.set_next(ValidateHandler()).set_next(LogHandler())
auth.handle({'auth':True,'valid':True})
Handlers chained. Each handles or passes to next. Adding handler = new class, no existing changes.
Prevention
Chain of Responsibility passes request along chain until handler processes it.
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