Difference between creational vs structural vs behavioral design patterns
Structural design patterns and behavioral design patterns are two categories of design patterns in software engineering that address different aspects of software design.
a. Structural Design Patterns:
Structural design patterns are concerned with the composition of classes or objects to form larger structures. They focus on simplifying the structure of the code, making it more efficient, flexible, and maintainable. These patterns deal with the relationships between classes and objects, providing guidelines for creating class hierarchies, managing relationships, and composing objects into larger structures.
Common structural design patterns include:
1. Adapter Pattern: Allows the interface of an existing class to be used as another interface. It is often used to make existing classes work with others without modifying their source code.
2. Bridge Pattern: Separates abstraction from implementation so that the two can vary independently. It involves creating a bridge interface that contains an implementation object, allowing them to evolve independently.
3. Composite Pattern: Composes objects into tree structures to represent part-whole hierarchies. It allows clients to treat individual objects and compositions of objects uniformly.
4. Decorator Pattern: Attaches additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.
5. Facade Pattern: Provides a simplified interface to a set of interfaces in a subsystem, making it easier to use and reducing dependencies.
6. Flyweight Pattern: Minimizes memory usage or computational expenses by sharing as much as possible with related objects. It is used to support a large number of fine-grained objects efficiently.
7. Proxy Pattern: Provides a surrogate or placeholder for another object to control access to it. It is useful when you want to add additional functionality to an object, such as lazy loading or access control.
b. Behavioral Design Patterns:
Behavioral design patterns are concerned with the interaction between objects, responsibilities, and algorithms. They define ways in which objects can communicate and collaborate to achieve a more flexible and efficient system. Behavioral patterns focus on the delegation of responsibilities among objects and how they collaborate at runtime.
Common behavioral design patterns include:
1. Chain of Responsibility Pattern: Passes a request along a chain of handlers. Each handler decides either to process the request or to pass it to the next handler in the chain.
2. Command Pattern: Encapsulates a request as an object, allowing for parameterization of clients with different requests, queuing of requests, and logging of the parameters for requests.
3. Interpreter Pattern: Defines a grammar for interpreting a language and provides an interpreter to interpret sentences in the language.
4. Iterator Pattern: Provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
5. Mediator Pattern: Defines an object that centralizes communication between objects in a system. It reduces direct connections between components and promotes loose coupling.
6. Memento Pattern: Captures and externalizes an object’s internal state so that the object can be restored to this state later.
7. Observer Pattern: Defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
8. State Pattern: Allows an object to alter its behavior when its internal state changes. The object appears to change its class.
9. Strategy Pattern: Defines a family of algorithms, encapsulates each algorithm, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
10. Template Method Pattern: Defines the skeleton of an algorithm in the superclass but lets subclasses override specific steps of the algorithm without changing its structure.
11. Visitor Pattern: Represents an operation to be performed on elements of an object structure. It lets you define a new operation without changing the classes of the elements on which it operates.
Both structural and behavioral design patterns are essential for creating well-organized, maintainable, and extensible software systems. They provide solutions to recurring problems and help developers follow best practices in software design. The choice of which pattern to use depends on the specific requirements of the system and the problems being addressed.