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The mnemonic acronym SOLID incorporates a set of software principles of object-oriented design. Originally introduced by Robert C. Martin in his 2000 paper “Design Principles and Design Patterns”, and later turned into an acronym by Michael Feathers, the ingredients of SOLID are:
- Single responsibility principle
- Open-closed principle
- Liskov substitution principle
- Interface segregation principle
- Dependency inversion principle
CUPID is the creation of Dan North, originating as a criticism of the SOLID principles above. CUPID principles have the same basic philosophy as SOLID: when coding, think about the people who will come after you.
- Composable
- Unix
- Predictable
- Idiomatic
- Domain-based
GRASP stands for general responsibility assignment software patterns and is a collection of, “nine fundamental principles in object design and responsibility assignment”, as described by Craig Larman in his book Applying UML and Patterns (1997).
- Creator – Who creates an object or a new instance of a class?
- Information Expert – What responsibilities can be assigned to an object?
- Low Coupling – How are objects connected to each other? How do you support low dependency, low change impact, and increased reuse?
- Controller – How are requests delegated from UI layer objects to domain layer objects, including coordinating the system operation?
- High Cohesion – How are the operations of elements functionally related? How do you keep objects focused, understandable, and manageable, (including supporting Low Coupling)?
- Polymorphism – How do you handle alternative elements based on type? How do you create pluggable software components?
- Indirection – Focused on avoiding a direct coupling between two or more elements through the use of intermediate units to handle inter-element communication, so as to avoid a direct connection.
- Pure Fabrication – Called a ‘service’ in domain-driven design, this class does not represent anything from the problem domain but is created to ensure High Cohesion and Low Coupling are achieved.
- Protected Variations – Designing objects, subsystems, and systems so that variations in these elements does not impact on other elements?