list all design patterns

Design patterns are essential tools in software development, providing solutions to common design challenges. They help developers communicate more effectively, enhance code maintainability, and facilitate collaboration. Below is a comprehensive list of widely recognized design patterns, categorized into three main types: Creational, Structural, and Behavioral patterns.

Comprehensive List of Design Patterns

1. Creational Design Patterns

Creational patterns focus on object creation mechanisms, allowing for greater flexibility and reuse of existing code. Key patterns include:

• Singleton: Ensures a class has only one instance and provides a global point of access to it.
• Factory Method: Defines an interface for creating objects but allows subclasses to alter the type of objects that will be created.
• Abstract Factory: Provides an interface for creating families of related or dependent objects without specifying their concrete classes.
• Builder: Separates the construction of a complex object from its representation, allowing for different representations to be created.
• Prototype: Creates new objects by copying an existing object, known as the prototype.

Example of Creational Patterns: | Pattern | Description | |---------------------|--------------------------------------------------------------------------------------------------------| | Singleton | Restricts instantiation of a class to a single instance. | | Factory Method | Delegates the responsibility of object creation to subclasses. | | Abstract Factory | Creates families of related or dependent objects without specifying their concrete classes. | | Builder | Constructs complex objects step by step. | | Prototype | Clones existing objects to create new ones. |

2. Structural Design Patterns

Structural patterns deal with object composition, providing ways to combine objects to form larger structures. Key patterns include:

• Adapter: Allows incompatible interfaces to work together by wrapping an existing class with a new interface.
• Bridge: Separates an object’s interface from its implementation, allowing them to vary independently.
• Composite: Composes objects into tree structures to represent part-whole hierarchies, allowing clients to treat individual objects and compositions uniformly.
• Decorator: Attaches additional responsibilities to an object dynamically without modifying its structure.
• Facade: Provides a simplified interface to a complex subsystem.
• Flyweight: Reduces the cost of creating and manipulating a large number of similar objects by sharing them.

Example of Structural Patterns: | Pattern | Description | |---------------|-----------------------------------------------------------------------------------------------------------| | Adapter | Allows two incompatible interfaces to communicate. | | Bridge | Separates interface and implementation to allow for independent variation. | | Composite | Creates a structure of objects recursively, allowing complex tree structures. | | Decorator | Adds new functionality to an object without altering its structure. | | Facade | Simplifies the interface to a subsystem, making it easier to use. | | Flyweight | Minimizes memory usage by sharing objects. |

3. Behavioral Design Patterns

Behavioral patterns focus on communication between objects, helping to define how objects interact in a system. Key patterns include:

• Observer: Defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified.
• Strategy: Defines a family of algorithms, encapsulates each one, and makes them interchangeable. This allows algorithms to vary independently from clients that use them.
• Command: Encapsulates a request as an object, thereby allowing parameterization of clients with queues, requests, and operations.
• Chain of Responsibility: Passes a request along a chain of handlers, allowing multiple objects to handle the request without the sender needing to know which object handles it.
• State: Allows an object to alter its behavior when its internal state changes, appearing as if it changed its class.
• Visitor: Represents an operation to be performed on the elements of an object structure, allowing you to define new operations without changing the classes of the elements.

Example of Behavioral Patterns: | Pattern | Description | |---------------------|---------------------------------------------------------------------------------------------| | Observer | Notifies multiple observers about changes in state. | | Strategy | Enables selecting an algorithm's behavior at runtime. | | Command | Treats requests as objects, allowing operations to be parameterized and executed independently. | | Chain of Responsibility | Passes a request along a chain of handlers, allowing multiple responses to respond to a request. | | State | Transitions early state changes, altering behavior without changing an object's type. | | Visitor | Enables adding new operations to a structure without modifying its classes. |

Conclusion

Understanding and utilizing design patterns is crucial for effective software engineering. These patterns provide proven solutions to common problems, making it simpler to develop scalable, maintainable, and robust systems. Whether you're working with Creational, Structural, or Behavioral patterns, adopting a design pattern approach can greatly enhance your development workflow and code quality.

For further reading and detailed explanations of each pattern, you can refer to resources like Refactoring.Guru and SourceMaking.