GRASP and Core Heuristics

GRASP and Core Heuristics

GRASP (General Responsibility Assignment Software Patterns) guides how to assign responsibilities to classes during object design.

Core GRASP Patterns

1. Information Expert: Assign responsibility to the class that possesses the necessary information to fulfill it.
2. Creator: Assign creation of object B to class A if A aggregates, contains, or records B.
3. Controller: Non-UI class coordinating system operations and workflow events.
4. Low Coupling: Organize responsibilities to keep inter-class dependencies minimal.
5. High Cohesion: Ensure the responsibilities of each class are focused and closely related.
6. Polymorphism: Assign varying behavior to polymorphic classes rather than conditional statements.
7. Pure Fabrication: Create an artificial domain class (e.g., DatabaseService, Logger) purely to achieve high cohesion and low coupling.
8. Protected Variations: Shield points of anticipated change with stable interfaces.

Pragmatic Design Heuristics

• DRY (Don’t Repeat Yourself): Every piece of knowledge must have a single, unambiguous representation in a system.
• YAGNI (You Aren’t Gonna Need It): Do not add speculative functionality until strictly needed.
• KISS (Keep It Simple, Stupid): Favor the simplest design that completely satisfies requirements.
• Hollywood Principle: “Don’t call us, we’ll call you”—framework inversion of control.