Exercise 1: Basic Decorator

The scenario

You are building a notification system. The core object is a Notifier that sends messages to users:

class EmailNotifier(Notifier):
    def send(self, recipient: str, message: str) -> None:
        print(f"EMAIL to {recipient}: {message}")

The system works fine. But now two new requirements arrive:

• Every notification should be logged (print when it is sent and to whom).
• Some notifications should have their message uppercased before sending (for urgent alerts).

You must add these behaviours without modifying EmailNotifier.

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Your task

Part A — add logging

Implement LoggingDecorator. It should:

• Print "SENDING notification to {recipient}" before the notification is sent.
• Print "SENT notification to {recipient}" after the notification is sent.
• Otherwise delegate to the wrapped notifier.

Expected output:

SENDING notification to alice@example.com
EMAIL to alice@example.com: Meeting at 3pm
SENT notification to alice@example.com

Part B — add uppercasing

Implement UppercaseDecorator. It should:

• Convert message to uppercase before passing it to the wrapped notifier.
• Not change recipient.

Expected output when wrapping EmailNotifier directly:

EMAIL to bob@example.com: SERVER IS DOWN

Part C — compose them

Wrap EmailNotifier with both decorators so that the message is uppercased and the send is logged.

Expected output:

SENDING notification to bob@example.com
EMAIL to bob@example.com: SERVER IS DOWN
SENT notification to bob@example.com

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Skeleton

See exercise1.py.

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What to focus on

• The decorator must implement the same interface as the object it wraps.
• The decorator receives the wrapped object in its constructor.
• Each decorator does exactly one thing.

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Solution · Exercise 2