Order Status Observers

Hard ⏱ 18 min 32% acceptance ★★★★☆ 4.2

Build a minimal observer pattern: OrderTracker has subscribe(callback) and update(status) — updating stores the status and calls every subscribed callback with it. Write it so callbacks added later miss earlier statuses (no replay). Demonstrate with a list-appending callback.

Examples

Example 1

Input

t = OrderTracker(); log = []; t.subscribe(log.append); t.update('packed'); log

Output

['packed']

Explanation

The callback fired on update.

Constraints

Support multiple subscribers.
update calls each with the new status.

Topics

OOPobserver pattern

Companies

ZomatoSwiggyDoorDash

Hints

Hint 1

Store callbacks in a list.

Hint 2

Loop and call them inside update.

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