Null Object pattern in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a Null Object class that implements the same interface.

LLD

class NullLogger:
    def log(self, message):
        [1]

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Apass

Bprint(message)

Creturn message

Draise Exception('Not implemented')

Attempts:

3 left

💡 Hint

Common Mistakes

Using print or return instead of pass.

The Null Object's method should do nothing, so pass is correct.

2fill in blank

medium

Complete the code to use the Null Object pattern to avoid null checks.

LLD

def process(logger):
    logger.[1]('Start processing')

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Alog

Bwrite

Cprint

Dsend

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names not defined in the interface.

The method to call on the logger is log as defined in the interface.

3fill in blank

hard

Fix the error in the Null Object implementation to correctly override the interface method.

LLD

class NullNotifier:
    def notify(self):
        [1]

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Araise NotImplementedError()

Bprint('Notification sent')

Creturn True

Dpass

Attempts:

3 left

💡 Hint

Common Mistakes

Raising exceptions or printing output in Null Object methods.

The Null Object should override the method and do nothing, so pass is correct.

4fill in blank

hard

Fill both blanks to complete the factory method that returns a Null Object when input is None.

LLD

def get_logger(logger):
    if logger is None:
        return [1]()
    else:
        return [2]

Drag options to blanks, or click blank then click option'

ANullLogger

Blogger

CLogger

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Returning None instead of Null Object instance.

If logger is None, return an instance of NullLogger, else return the given logger.

5fill in blank

hard

Fill all three blanks to implement a Null Object pattern with a dictionary comprehension filtering active users.

LLD

active_users = {user: [1] for user, status in users.items() if status [2] 'active' and user != [3]

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ANullNotifier()

B==

CNone

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong operators or values in comprehension.

Assign NullNotifier() as the value, filter users where status is 'active', and exclude users equal to None.