Design Patterns en Programmation

Design Patterns

• Créational Patterns focus on object creation mechanisms while decoupling systems from concrete classes.
• Factory Pattern: Creates objects from a family without relying on concrete classes. Example: A "Carpenter" class creating furniture in different styles (modern, art deco, antique).
• Builder Pattern: Constructs complex objects step-by-step, avoiding telescoping constructors with numerous parameters. Example: Pizza creation with defined steps (dough, base, toppings).
• Singleton Pattern: Guarantees a class has only one instance and provides a global access point. Common for resource or configuration managers.
• Prototype Pattern: Creates objects by copying existing instances, independent of their concrete classes. Example: Java's clone() method for shallow or deep cloning.

Structural Patterns

• Structural Patterns deal with object composition and organization into complex structures while maintaining flexibility.
  • Adapter Pattern: Converts one interface into another expected by a client. Example: Adapt JSON files to XML libraries.
  • Composite Pattern: Structures objects hierarchically (tree-like) to manipulate both leaf nodes and composite nodes uniformly. Example: File systems (files and folders).
  • Decorator Pattern: Dynamically adds functionalities to objects. Example: Cars with different options (e.g. diesel, turbo).
  • Proxy Pattern: Provides a placeholder for another object to control access, reduce costs, or add functionalities. Example: Security proxy or remote proxy for heavy objects.
  • Facade Pattern: Offers a simplified interface for interacting with a complex system. Example: Video applications using multiple libraries.

Behavioral Patterns

• Behavioral Patterns define how objects interact and distribute responsibilities.
  • Template Method Pattern: Establishes an algorithm's skeleton in a superclass, with specific steps redefined in subclasses. Example: File processing (PDF, DOC, CSV) with shared and specific steps.
  • Strategy Pattern: Defines a family of interchangeable algorithms, dynamically selectable. Example: Different route options (bicycle, car, walking) in a GPS application.
  • State Pattern: Changes an object's behavior based on its state without altering its instance. Example: Subway gate states (open, closed, locked).
  • Command Pattern: Encapsulates a request as an object, allowing for queuing, scheduling, or undo functionalities. Example: Menu buttons in GUI applications.
  • Visitor Pattern: Separates algorithm from objects on which it operates, facilitating addition of new operations. Example: Exporting data to XML, JSON, or YAML without modifying the data classes.