Design Patterns

Unified Solutions for Software Problems

Design patterns are tried-and-true, reusable solutions to common problems in software design. They were first defined in the seminal book, “Design Patterns: Elements of Reusable Object-Oriented Software,” by authors Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, collectively known as the Gang of Four (GoF).

Categories of Design Patterns:

1. Creational Patterns:

Focus on object creation mechanisms, enhancing flexibility and reusability.

Examples include:

-Simple Factory

Used to create objects of a specific type without needing to know how they are created.

-Abstract Factory

Creates families of related objects without specifying their concrete classes.

-Builder

 Constructs complex objects step by step.

-Prototype

Creates new objects by copying an existing object.

-Singleton

 Ensures a class has only one instance.

2. Structural Patterns:

Aim to simplify design by establishing straightforward ways to build complex relationships between objects.

Examples include:

-Adapter

Makes two incompatible objects work together.

-Bridge

Separates an object’s interface from its implementation.

-Composite

 Treats a group of objects as a single object.

-Decorator

 Adds new functionalities to an object without altering its structure.

-Facade

Provides a simple interface to a complex system of objects.

-Flyweight

 Reduces memory usage by sharing as much state as possible with other similar objects.

-Proxy

Controls access to another object.

3. Behavioral Patterns:

Focus on improving communication between disparate objects, facilitating how objects interact and distribute responsibilities among them.

Examples include:

- Chain of Responsibility

 Passes a request along a chain of objects until it is handled.

-Command

Executes a request without knowing the requester.

-Interpreter

Parses a series of symbols into a structured data format.

-Mediator

 Facilitates communication between objects without them needing to be aware of each other.

-Memento

 Saves and restores an object’s state.

-Observer

Notifies objects about changes in another object.

-State

Changes an object’s behavior based on its current state.

-Strategy

 Defines an object’s behavior without changing its class.

-Template Method

Defines the skeleton of an algorithm, allowing subclasses to alter some steps.

-Visitor

Allows for new operations to be defined on a data structure without changing its elements.

The Importance of Design Patterns:

Improves Code Maintainability and Comprehension

Design patterns enhance the readability and maintainability of code by offering clear, tested solutions to common problems.

Facilitates Code Reusability and Abstraction

 By abstracting away details, design patterns make applications more adaptable to future changes.

Eases Communication Among Developers

When working in teams, design patterns provide a shared language to discuss complex solutions more effectively

Minimizes Potential Design Errors

Leveraging proven and tested solutions can cover common scenarios and reduce the likelihood of errors in the design phase.

Through a practical example in C#, consider a scenario where we have an old system handling data in XML format, but we aim to upgrade the system to interact with a new service using JSON format. Instead of overhauling the entire old system, we could employ the Adapter Pattern to bridge the gap between the old system and the new service, showcasing how design patterns can ease the transition between different data formats and system interfaces, increasing code flexibility and maintainability without the need for extensive rewrites.
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