Skip to main content

SOLID (4/5) - Interface segregation principle

Interface segregation principle


In the field of software engineering, the interface-segregation principle (ISP) states that no client should be forced to depend on methods it does not use. ISP splits interfaces that are very large into smaller and more specific ones so that clients will only have to know about the methods that are of interest to them. Such shrunken interfaces are also called role interfaces. ISP is intended to keep a system decoupled and thus easier to refactor, change, and redeploy.

using System;

namespace interfacesegregation
{
    public class Document 
    {

    }

    public interface IMachine 
    {
        void Print(Document d);
        void Scan(Document d);
        void Fax(Document d);
    }

    public class MultiFunctionPrinter : IMachine 
    {
        public void Print(Document d
        {
            //
        }

        public void Scan(Document d)
        {
            //
        }

        public void Fax(Document d)
        {
            //
        }
    }

    // The interface has too much functionaly that won't be used
    public class Printer : IMachine 
    {
        public void Print(Document d
        {
            //
        }

        public void Scan(Document d)
        {
            throw new NotImplementedException();
        }

        public void Fax(Document d)
        {
            throw new NotImplementedException();
        }
    }    

    // We should separate the interface into smaller ones 
    public interface IPrinter 
    {
        void Print(Document d);
    }

    public interface IScanner 
    {
        void Scan(Document d);
    }

    public class Photocopier : IPrinterIScanner
    {
        public void Print(Document d
        {
            //
        }

        public void Scan(Document d)
        {
            //
        }
    }

    public interface IMultiFunctionDevice : IPrinterIScanner
    {        
    }

    public class MultiFunctionMachine : IMultiFunctionDevice
    {
        public void Print(Document d
        {
            Console.WriteLine("Printing...");
        }

        public void Scan(Document d)
        {
            Console.WriteLine("Scanning...");
        }
    }


    public class Program
    {
        static void Main(string[] args)
        {
            var machine = new MultiFunctionMachine();
            machine.Scan(new Document());
            machine.Print(new Document());
        }
    }
}

Comments

Popular posts from this blog

C# Extension Methods

 C# Extension Methods Extension methods      public   static   class   ExtensionMethods     {          public   static   Stopwatch   Measure ( this   Func < int >  f )         {              var   sw  =  new   Stopwatch ();              sw . Start ();              f ();              sw . Stop ();              return   sw ;         }          public   static   void   Save ( this   ISerializable   s...

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...