Fundamentals

Principles of Computer Science and Programming

---

1 SOLID Principles

1-1 Single Responsibility Principle:

A class should only have one reason to change; Separation of concerns.

A class should have only a single responsibility — that is, only changes to one part of the software's specification should be able to affect the specification of the class.

1-2 Open-Closed Principle:

Classes should be open for extension but closed for modification.

Software entities should be open for extension, but closed for modification.

1-3 Liskov Substitution Principle:

You should be able to substitute a base type for a subtype.

Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program.

1-4 Interface Segregation Principle:

Don't put too much into an interface; YAGNI; split into separate interfaces.

1-5 Dependency Inversion Principle:

High-level modules should not depend upon low-level ones; use abstraction.

Entities must depend on abstractions, not on concrete implementations.

---

2 Design Patterns

2-1 Creational Patterns:

The construction (creation) of objects.

2-1-1 Builder

Used when object construction is complicated. It's piecewise.

2-1-2 Factory Method

2-1-3 Abstract Factory

Used when object creation logic becomes too convoluted and the constructor is not descriptive. It's non-piecewise. Can be outsourced (A separate function, a separate class, hierarchy of factories). A component responsible solely for the wholesale (not piecewise) creation of objects.

2-1-4 Prototype

A partially or fully initialized object that you copy (clone) and make use of.

2-1-5 Singleton

A component which is instantiated only once.

2-2 Structural Patterns:

The structure of classes (e.g. class members).

2-3 Behavioral Patterns:

No central theme (they are all different).

---