Skip to main content

Factory Pattern

Factory Pattern 


Gamma Categorization: Creational Design Patten
Summary: When the object construction is complicated, needing multiple arguments, we should create a separate function (Factory Method) or class (Factory), which is responsible for the creation of the entire object.

Problem examples

Suport of multiple databases
Multiple data sources: Serial port, ethernet port, device driver
Diferent report types

    Solution

    Abstract class
    Generalized interface
    A Factory creates instances of the concrete classes

    Sample Code

    Problem: we need to create a Point object, that may be either Cartesian or Polar.

    Factory Method Solution

    public class Point
    {
        private double x,  y;
        private Point (double x, double y)
        {
            this.x = x;
            this.y = y;
        }

        public static Point NewCartesianPoint(double x, double y)
        {
            return new Point(x, y);
        }

        public static Point NewPolarPoint(double rho, double theta)
        {
            return new Point(rho*Math.Cos(theta), rho*Math.Sin(theta));
        }

        public override string ToString() 
        {
            return $"x: {x}, y: {y}";
        }
    }

    Usage

    var point = Point.NewCartesianPoint(10,20);
    System.Console.WriteLine(point);

    Factory Class Solution

    public class PointFactory
    {
        public static Point NewCartesianPoint(double x, double y)
        {
            return new Point(x, y);
        }

        public static Point NewPolarPoint(double rho, double theta)
        {
            return new Point(rho*Math.Cos(theta), rho*Math.Sin(theta));
        }
    }

    public class Point
    {
        private double x,  y;
        public Point (double x, double y)
        {
            this.x = x;
            this.y = y;
        }

        public override string ToString() 
        {
            return $"x: {x}, y: {y}";
        }
    }

    Usage

    var point = PointFactory.NewCartesianPoint(10,20);
    System.Console.WriteLine(point);

    Comments

    Post a Comment

    Popular posts from this blog

    XML Webservice (ASMX) - SOAP Request and Response Invocation logging

    You are an integration developer. Eventualy you came into the state where there is nothing else you can debug, and you have to check which SOAP request it is built on the request, and which SOAP response you are getting from the server. C# XML Webservice (ASMX) - SOAP Request and Response Invocation logging In the legaccy .NET framework System.Web.Services , this means using soapExtensions to help you intersept the interaction with the webservice. This is done like so:  public class TraceExtension : SoapExtension     {         Stream oldStream;         Stream newStream;         string filename;         // Save the Stream representing the SOAP request or SOAP response into          // a local memory buffer.          public override Stream ChainStream(Stream stream)         {           ...
    Post a Comment
    Read more

    Abstract Factory Pattern

    Abstract Factory Pattern  Gamma Categorization: Creational Design Patten Summary: When the object construction is complicated, needing multiple arguments, we should create a separate function (Factory Method) or class (Factory), which is responsible for the creation of the all object. Problem examples Suport of multiple databases Multiple data sources: Serial port, ethernet port, device driver Diferent report types Solution Abstract class Generalized interface A Factory creates instances of the concrete classes Sample Code The abstract factory public   interface   IPhotoFactory {      IAnaloguePhoto   CreateAnaloguePhoto ();      IDigitalPhoto   CreateDigitalPhoto (); } The abstract products public   interface   IAnaloguePhoto {      string   GetName (); } public   interface   IDigitalPhoto {      ...
    Post a Comment
    Read more

    SOLID (1/5) - Single Resposibility Principle

     SOLID (1/5) - Single Resposibility Principle The single-responsibility principle (SRP) is a computer-programming principle that states that every class in a computer program should have responsibility over a single part of that program's functionality, which it should encapsulate. All of that module, class or function's services should be narrowly aligned with that responsibility. In the following example we have a TodoList class which only handles it's own functionality logic, and then we have a Persistance class which handles the saving logic, hence keeping the concerns separeted. using   System ; using   System . Collections . Generic ; namespace   Journal {      public   class   TodoList     {          private   readonly   List < string >  _entries  =  new   List < string >();          private...
    Post a Comment
    Read more