Applying Memento and Observer Patterns in MQL5
Summary
The article presents two behavioral software design patterns through MQL5 examples. Memento stores an object's state as a snapshot so it can later be restored, while keeping the object's internal state behind a limited interface. The article notes potential costs, including copying large states and maintaining only a limited snapshot history. Its example separates the state holder, the object that creates or restores snapshots, and a caretaker that manages the saved object.
Observer defines a one-to-many relationship in which a subject notifies dependent objects when its state changes. The MQL5 example uses an observer interface and subject methods for attaching, detaching, and notifying observers. The author highlights reduced coupling and broadcast updates, while noting that large update cascades and debugging can be difficult. These are programming patterns intended to support reusable and maintainable software; the examples do not evaluate a trading strategy or report empirical trading results.
Key ideas
- Memento captures an object's state for later restoration while limiting direct exposure of its internals.
- Large snapshots can be costly, and a bounded set of saved states limits available history.
- Observer lets a subject notify multiple dependent objects when its state changes.
- MQL5 examples show snapshot management and observer attachment, removal, and notification.
- Observer updates can be hard to debug, particularly when many objects receive changes.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.