Design patterns
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This document discusses various design patterns for software engineering. It describes creational patterns like factory method, abstract factory, builder, singleton, and prototype that deal with object creation. It also covers structural patterns like adapter, bridge, composite, decorator, facade, flyweight, and proxy that focus on class and object composition. Additionally, it mentions behavioral patterns like chain of responsibility, command, iterator, mediator, template method, visitor, memento, observer, state, and strategy that are related to communication between objects. The document provides examples of when and how to use different design patterns to solve common programming problems.
Design patterns
- 1. Design Patterns for software engineering Presented by: Rohan Jain Tanisha Bhayani Akshay Bhanderi Abhay Desale
- 2. What is design pattern? ● Design patterns are typical solutions to commonly occurring problems in software design. ● They are like pre-made blueprints that you can customize to solve a recurring design problem in your code. ● Types of design pattern ○ Creational Design Patterns ○ Structural Design Patterns ○ Behavioral Design Patterns
- 3. Creational Design Pattern: Factory Method we create object without exposing the creation logic to client and the client use the same common interface to create new type of object
- 4. Creational Design Pattern:Abstract Factory Lets you produce families of related objects without specifying their concrete classes.
- 5. Creational Design Pattern: Builder ● That lets you construct complex objects step by step. ● The pattern allows you to produce different types and representations of an object using the same construction code.
- 6. Creational Design Pattern: Singleton class Database is private static field instance: Database private constructor Database() is public static method getInstance() is if (Database.instance == null) then acquireThreadLock() and then if (Database.instance == null) then Database.instance = new Database() return Database.instance public method query(sql) is class Application is method main() is Database foo = Database.getInstance() foo.query("SELECT ...") // ... Database bar = Database.getInstance() bar.query("SELECT ...") // The variable `bar` will contain the same object as // the variable `foo`. That lets you ensure that a class has only one instance, while providing a global access point to this instance.
- 7. Creational Design Pattern: Prototype lets you copy existing objects without making your code dependent on their classes.
- 8. Structure Design Pattern: Adapter Pattern Scenario: Two incompatible interfaces but the core functionality is same. Class Adapter - Inheritance Object Adapter - Delegation through Composition
- 9. Structure Design Pattern: Bridge Pattern Scenario: Vary the implementation and the abstraction by placing the two into separate class hierarchies.
- 10. Structure Design Pattern: Composite Pattern Scenario: When clients ignore the difference between compositions of objects and individual objects.
- 11. Structure Design Pattern: Decorator Pattern Scenario: Allows behavior to be added to an individual object, dynamically, without affecting the behavior of other objects from the same class.
- 12. Structure Design Pattern: Facade Pattern Scenario: The client facing interface needs simplification.
- 13. Structure Design Pattern: Flyweight Pattern Scenario: Minimize memory usage or computational expenses by sharing as much as possible with similar objects.
- 14. Structure Design Pattern: Proxy Pattern Scenario: When client needs to protect, hide complexity, or delay expensive actions.
- 15. Anti Pattern ● Applying a particular design pattern in the improper context.
- 16. Behaviour Pattern ● Behavioral design patterns are concerned with the interaction and responsibility of objects. Behaviour Design Pattern: Chain of Responsibility What it suggests? Pass the request along the chain of handlers instead of one. Control order of request handling
- 17. Behaviour Design Pattern: Command What is suggets? Turns a request into a stand-alone object that contains all information about the request.
- 18. Behaviour Design Pattern: Iterator What is suggets? lets you traverse elements of a collection without exposing its underlying representation
- 19. Behaviour Design Pattern: Meditor What is suggets? This pattern restricts direct communications between the objects and forces them to collaborate only via a mediator object. Increases reusability
- 20. Behaviour Design Pattern: Template Method What it says? Just define the skeleton of a function in an operation, deferring some steps to its subclasses. Remove duplication
- 21. Behaviour Design Pattern: Visitor What is says? Visitor lets you define a new operation without changing the classes of the elements on which it operates.
- 22. Behaviour Design Pattern: Memento Lets you save and restore the previous state of an object without revealing the details of its implementation.
- 23. Behaviour Design Pattern: Observer Lets you define a subscription mechanism to notify multiple objects about any events that happen to the object they’re observing.
- 24. Behaviour Design Pattern: State Lets an object alter its behavior when its internal state changes. It appears as if the object changed its class.
- 25. Behaviour Design Pattern: Strategy Lets you define a family of algorithms, put each of them into a separate class, and make their objects interchangeable. Problem Solution
- 26. References ● https://refactoring.guru/design-patterns ● https://www.javatpoint.com/design-patterns-in-java ● https://sourcemaking.com/design_patterns ● https://www.youtube.com/watch?v=TeZqKnC2gvA (for visiter) ● https://www.youtube.com/watch?v=7Pj5kAhVBlg ● https://medium.com/educative/the-7-most-important-software-design-patterns-d60e546afb0e ● https://medium.com/federicohaag/coding-better-using-design-patterns-4d7385a9e7ac ● https://www.youtube.com/watch?v=v9ejT8FO-7I&list=PLrhzvIcii6GNjpARdnO4ueTUAVR9eMBpc(Design Pattern Series) ● https://en.wikipedia.org/wiki/Structural_pattern ● https://stackoverflow.com/questions/980601/what-is-an-anti-pattern ● https://dev.to/carlillo/design-patterns---adapter-2pi3 ● https://stackoverflow.com/questions/319728/when-do-you-use-the-bridge-pattern-how-is-it-different-from- adapter-pattern ● https://en.wikipedia.org/wiki/Composite_pattern ● https://en.wikipedia.org/wiki/Decorator_pattern ● https://en.wikipedia.org/wiki/Facade_pattern ● https://www.oreilly.com/library/view/learning-javascript-design/9781449334840/ch09s18.html ● http://www.cs.sjsu.edu/faculty/pearce/modules/patterns/distArch/proxy.htm