Design Patterns: Proven Solutions

Design patterns are typical solutions to common problems in software design. They are like blueprints that you can customize to solve a specific design problem.

1. Creational: Singleton

Ensures a class has only one instance and provides a global point of access to it.

• Use Case: Database connections, Logging services.

2. Creational: Factory Method

Provides an interface for creating objects but allows subclasses to alter the type of objects that will be created.

• Use Case: A library where users can choose between different types of file exporters (PDF, CSV, HTML).

3. Structural: Adapter

Allows objects with incompatible interfaces to collaborate.

• Use Case: Integrating a 3rd party legacy library into your modern codebase.

4. Behavioral: Observer

Defines a subscription mechanism to notify multiple objects about any events that happen to the object they’re observing.

• Use Case: Event listeners in Javascript or a Newsletter system.

5. Behavioral: Strategy

Defines a family of algorithms, puts each of them into a separate class, and makes their objects interchangeable.

• Use Case: A shopping cart that can use different payment methods (PayPal, Credit Card, Crypto).

The Danger of Over-Engineering

Design patterns are tools, not goals. Don't force a pattern into a simple problem just for the sake of using it. Start simple and refactor to a pattern only when the complexity warrants it.