Design Patterns

Node.js nut-ioc usage

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nut-ioc npm package is a simple, lightweight and fast IoC Container Framework.

nut-ioc injects dependencies run-time so that developers don't need to require modules.

Developers can implement in their codes following OOP basics, principles, patterns and concepts and probably more than that 🙂

  • Separation of Concern(SoC)
  • Single Responsibility Principle(SRP)
  • Open Closed Principle
  • Dipendency Inversion(Injection) Principle(DIP)
  • Chain of Responsibility Pattern
  • Aspect Oriented Programming

you can reach github repository.

https://github.com/nodejs-projects-kenanhancer/nut-ioc

Installing nut-ioc with npm

npm i nut-ioc

Demo GitHub Repository

You can find different usages of nut-ioc framework in separate brances.

https://github.com/nodejs-projects-kenanhancer/nut-ioc-basic-demo.git

Branch list
load-dependencies-with-dependencyPath
load-dependencies-with-dependencyPath-and_dynamically
load-dependencies-with-different-loaders
load-dependencies-with-interceptors
load-dependencies-with-new-loaders-and-filters
load-dependencies-with-programatic-notation
nut-swagger-usage
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Node.js nut-pipe usage

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nut-pipe npm package is an implementation of Chain of Responsibility Pattern. We can encapsulate or wrap every aspect of code in separate module or class or function, etc. So that, separated aspect modules would implement Single Responsibility Principle(SRP) and Seperation of Concern Principle(SoC) properly.

🙂 so if you want to implement OOP basics and principles, then you can use nut.pipe npm package.

This design provides to developer clean business logic code. They don't need to think about Error, Exception, Log handling business logic. Before their business logic code is called, pipeline is called and it means first middleware is triggered then first middleware will trigger next one, but no middleware knows about next middleware. Middleware should know about its business logic then should call next one.

I know too much words but developers want to see code 🙂 same code will be developed in different ways.

Code example v1

I wrote a greeting service with sayHello() and sayGoodbye() functions. They include all business logic in their body. This is not good approach definitely. Code duplications are everywhere 🙂 For example, every functions have try/catch, console.log('ENTRY: …'), console.log('SUCCESS: …'), console.log('ERROR: …'), etc. Notice that getFullName doesn't contain these business logics. So, we can't know whether it is called or not. If developer like me 🙂 doesn't write these kind of aspects(logging and exception handling is kind of aspect) then we never understand that that method is called in run-time.

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Designing OOP Step by Step

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I read Head First Design Patterns book shown as below. It is pretty good reference of Design Patterns. If you want to be familiar of Design Patterns, i recommend it definitely. This post contains some examples of this book but in a different presentation. When I want to remember fundamentals of Design Patterns, this post will remind me 🙂 I hope that you will benefit from this post.

I will create a class diagram and improve it step by step.

If you don't want to read all paragraphs, you just view class diagrams and code samples step by step. But, i heavily recommend to read and think of this post 🙂

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C# Asynchronous Programming Patterns

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There are 3 Asynchronous Programming Patterns in C#.

1- Asynchronous Programming Model (APM)
2- Event-based Asynchronous Pattern (EAP)
3- Task-based Asynchronous Pattern (TAP)

 

1- Asynchronous Programming Model (APM)

Asynchronous Programming Model using Delegates

you can reach that article from Calling synchronous methods asynchronously

2- Event-based Asynchronous Pattern (EAP)

3- Task-based Asynchronous Pattern (TAP)

Chain of Responsibility Pattern and Aspect Oriented Programming with C#.NET

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Each class contains only the business logic code, while the aspects will be responsible of intercepting the code in order to inject the cross-cutting concerns.

This is first version of example code.

This is second version. You can find MethodInfo and parameter values in the aspect classes.

Gang of Four Patterns

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Creational Patterns

Creational patterns are ones that create objects for you, rather than having you instantiate objects directly. This gives your program more flexibility in deciding which objects need to be created for a given case.

  • Abstract factory: provide an interface for creating families of related or dependent objects without specifying their concrete classes.
  • Builder: separate the construction of a complex object from its representation, allowing the same construction process to create various representations.
  • Factory method: define an interface for creating a single object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.
  • Prototype: specify the kinds of objects to create using a prototypical instance, and create new objects from the 'skeleton' of an existing object, thus boosting performance and keeping memory footprints to a minimum.
  • Singleton: ensure a class has only one instance, and provide a global point of access to it.

Structural Patterns

These concern class and object composition. They use inheritance to compose interfaces and define ways to compose objects to obtain new functionality.

  • Adapter: allows classes with incompatible interfaces to work together by wrapping its own interface around that of an already existing class.
  • Bridge: decouples an abstraction from its implementation so that the two can vary independently.
  • Composite: composes zero-or-more similar objects so that they can be manipulated as one object.
  • Decorator: dynamically adds/overrides behaviour in an existing method of an object.
  • Facade: provides a simplified interface to a large body of code.
  • Flyweight: reduces the cost of creating and manipulating a large number of similar objects.
  • Proxy: provides a placeholder for another object to control access, reduce cost, and reduce complexity.

Behavioral Patterns

Most of these design patterns are specifically concerned with communication between objects.

  • Chain of responsibility: delegates commands to a chain of processing objects.
  • Command: creates objects which encapsulate actions and parameters.
  • Interpreter: implements a specialized language.
  • Iterator: accesses the elements of an object sequentially without exposing its underlying representation.
  • Mediator: allows loose coupling between classes by being the only class that has detailed knowledge of their methods.
  • Memento: provides the ability to restore an object to its previous state (undo).
  • Observer: is a publish/subscribe pattern which allows a number of observer objects to see an event.
  • State: allows an object to alter its behavior when its internal state changes.
  • Strategy: allows one of a family of algorithms to be selected on-the-fly at runtime.
  • Template: method defines the skeleton of an algorithm as an abstract class, allowing its subclasses to provide concrete behavior.
  • Visitor: separates an algorithm from an object structure by moving the hierarchy of methods into one object.