Design Patterns Cheat Sheet - Selecting the Appropriate Design Pattern

In system design, selecting the right design pattern is related to choosing the right tool for the job. It's essential for crafting scalable, maintainable, and efficient systems. Design patterns are reusable, proven solutions to common software design problems that help build scalable, maintainable, and efficient systems.

• Improve code readability and maintainability while promoting reusability and reducing duplication.
• Enable better team communication through shared and standard design terminology.

Example: The Factory Pattern is used to create objects without exposing the exact creation logic, making the system more flexible and loosely coupled.

Selecting the Appropriate Design Pattern

Before we select a pattern, we must identify and understand the problem we have encountered, and based on that we can choose which sub-category of design pattern we can go for.

Let us see in this Design Patterns Cheat Sheet, that in which scenario to choose which design pattern, that can effectively solve our problem:

Selecting the Appropriate Creational Design Patterns

Creational design patterns deal with object creation mechanisms and simplify the process of creating objects. They encapsulate object creation logic, making code more flexible, reusable, and loosely coupled.

• Provides flexibility by allowing object creation methods to be modified or extended easily.
• Includes common patterns such as Singleton, Factory, Abstract Factory, and Prototype.
• Improves code quality by enhancing maintainability, readability, and scalability.

We must choose Creational Design Patterns when the Problem is related to Object Creation.

• Singleton: Ensures only one instance of a class exists and provides a global access point to it.
• Factory Method: Lets subclasses decide which object to create, promoting loose coupling.
• Abstract Factory: Creates families of related objects without specifying their concrete classes.
• Prototype: Creates new objects by cloning an existing object (prototype).
• Builder: Constructs complex objects step by step, allowing different representations.

Selecting the Appropriate Structural Design Patterns

Structural design patterns focus on organizing classes and objects into larger structures while maintaining flexibility and efficiency. They help simplify relationships between components and make systems easier to extend and maintain.

• Promote code reuse by organizing classes and objects into efficient structures.
• Simplify system design and make complex systems easier to manage and understand.
• Support scalability and integration when adding new components or refactoring existing code.

We must choose Structural Design Patterns when the Problem is related to Object Assembly.

• Adapter: Acts as a bridge between two incompatible interfaces to make them work together.
• Bridge: Separates abstraction from implementation so both can vary independently.
• Composite: Treats individual objects and compositions of objects uniformly.
• Decorator: Dynamically adds new behaviors to objects without modifying their structure.
• Facade: Provides a simplified interface to a complex system.
• Flyweight: Reduces memory usage by sharing common data among multiple objects.
• Proxy: Controls and manages access to another object.

Selecting the Appropriate Behavioral Design Patterns

Behavioral design patterns focus on managing communication and interactions between objects. They help encapsulate varying behaviors, distribute responsibilities, and promote loose coupling within a system.

• Facilitate code reuse and flexibility by defining how objects interact and communicate.
• Improve maintainability by organizing responsibilities and behaviors effectively.
• Handle complex scenarios such as workflows, state transitions, and object communication.

We must choose Behavioral Design Patterns when the Problem is related to Object Interactions.

• Observer: Defines a one-to-many dependency so multiple objects get notified when one object changes state.
• Strategy: Encapsulates interchangeable algorithms and allows them to be swapped at runtime.
• Command: Encapsulates a request as an object, enabling parameterization and decoupled execution.
• State: Changes an object’s behavior based on its internal state.
• Visitor: Separates algorithms from object structures by adding new operations without modifying them.
• Memento: Captures and restores an object’s previous state without exposing its internal structure.
• Iterator: Provides a way to access elements of a collection sequentially without exposing its structure.
• Mediator: Centralizes communication between objects to reduce direct dependencies.
• Chain of Responsibility: Passes a request along a chain of handlers until one processes it.
• Template Method: Defines the skeleton of an algorithm, allowing subclasses to override specific steps.

Importance of Choosing the Right Design Pattern

According to this Design Patterns Cheat Sheet, choosing the right design pattern is crucial due to:

• Scalability: Ensures the architecture can accommodate growth without excessive restructuring.
• Flexibility: Enables easy adaptation to changing requirements and future enhancements.
• Maintainability: Facilitates code readability and comprehension, easing maintenance tasks.
• Reusability: Promotes reuse of proven solutions, saving development time and effort.
• Performance: Optimizes code execution and resource utilization for efficient operation.