fundamentals/object-relationships

Aggregation in class design implies a weak 'has-a' relationship where a child object can outlive its parent container, whereas composition enforces strict ownership and lifecycle dependency, meaning the child is destroyed when the parent is destroyed.

Dependency in object relationships indicates a temporary, weak coupling where one class merely uses another as a parameter or local variable, while association represents a stronger, permanent structural link where one class holds a direct reference to another as a field.

Use composition over aggregation for domain models when a child component's lifecycle is strictly bound to its parent container, ensuring the child cannot logically exist or operate independently without the parent object maintaining ownership.

Reduce accidental coupling during domain model design reviews by evaluating parent-child ownership rules, spotting complex message chains, and applying Hide Delegate refactoring nudges to simplify layered interactions and distinguish dependency from association.

Refactoring message chains clarifies object relationships by identifying unnecessary intermediary dependencies and offering Hide Delegate suggestions, which reduces needless structural coupling and keeps class diagrams readable and maintainable.