Introduction to Creational Patterns

Creational design patterns focus on object creation mechanisms, providing flexible and efficient ways to instantiate objects while abstracting the creation process. They address challenges like managing object initialization, controlling instantiation, and ensuring systems are loosely coupled. These patterns are particularly useful when the creation process is complex, needs to be reusable, or requires specific configurations.

Important Creational Patterns

1. Singleton Pattern
   • Purpose: Ensures a class has only one instance and provides a global point of access to it.
   • Use Case: When a single, shared resource is needed (e.g., a configuration manager or database connection pool).
   • Example: A logger class that maintains one instance across the application.
   • Pros: Controlled access, reduced memory usage.
   • Cons: Can introduce global state, making testing and concurrency harder.
2. Factory Method Pattern
   • Purpose: Defines an interface for creating objects but lets subclasses decide which class to instantiate.
   • Use Case: When the exact type of object needed depends on runtime conditions (e.g., creating platform-specific UI components).
   • Example: A document creator that produces PDF or Word documents based on user input.
   • Pros: Promotes loose coupling, supports open/closed principle.
   • Cons: Can lead to complex class hierarchies.
3. Abstract Factory Pattern
   • Purpose: Provides an interface for creating families of related or dependent objects without specifying their concrete classes.
   • Use Case: When a system needs to work with multiple product families (e.g., GUI frameworks for different operating systems).
   • Example: A UI toolkit creating buttons and windows tailored for Windows or macOS.
   • Pros: Ensures consistency across related objects, simplifies swapping product families.
   • Cons: Adding new product types can be cumbersome.
4. Builder Pattern
   • Purpose: Separates the construction of a complex object from its representation, allowing step-by-step creation.
   • Use Case: When an object requires extensive configuration or multiple construction steps (e.g., building a complex HTML document or a meal order).
   • Example: A house builder that constructs houses with varying features (walls, roof, etc.).
   • Pros: Fine-grained control over construction, reusable process.
   • Cons: Requires a separate builder class, can be overkill for simple objects.
5. Prototype Pattern
   • Purpose: Creates new objects by copying an existing object (prototype), avoiding the need for complex initialization.
   • Use Case: When object creation is expensive, and cloning is more efficient (e.g., duplicating a game character).
   • Example: A cell object that clones itself to create new cells with similar properties.
   • Pros: Reduces initialization overhead, supports dynamic object creation.
   • Cons: Deep copying can be complex, especially with circular references.

Why Use Creational Patterns?

• Flexibility: They decouple object creation from usage, making systems easier to extend or modify.
• Reusability: Standardize creation processes, reducing code duplication.
• Scalability: Handle complex instantiation logic without cluttering client code.
• Maintainability: Centralize creation logic, improving code organization.

When to Use?

• When object creation involves multiple steps or dependencies.
• When you need to enforce constraints on how objects are instantiated.
• When the type or number of objects created depends on runtime conditions.