Singleton pattern using baseclass

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Hi,

I want to save data in database in that i want to implement using Singleton pattern with base class can any body know please help me

Posted 13-Mar-11 23:40pm

Rupa1

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Albin Abel 14-Mar-11 6:14am

I hope you question is not "How to create a singleton class". Then explain how you want to use the singleton class. Without knowing this how we can answer?. Also have you tried anything

Rupa1 14-Mar-11 6:15am

yes i don't know please tell me sir

pankajupadhyay29 14-Mar-11 6:21am

what you don't know? To Create singleton class? else specify your scenario.

Rupa1 14-Mar-11 6:22am

because i searched in Google but i am not able to understand........

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Albin Abel · Answer 1 · 2011-03-14T06:10:00

In a simple way singleton object is the one which can have only one instance of it in the memory.

Look at the example below

C#

 public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
    private static Person person;
    private Person()
    {
    }
    public static Person GetPerson()
    {
        if (person == null)
        {
            person = new Person();
        }
        return person;
    }
}

This Person class you can't instantiate in the normal way like Person person=new Person() because of the private constructor. But you need to access it like Person person=Person.GetPerson() which always return the same instance till the static Person object in the memory.

It is the simplest form. Now how you want to use this pattern?.

_Ashish · Answer 2 · 2011-03-14T07:54:00

When you define a class, it means you can create a large number of its object at runtime. It is because of public constructor.

class Box {
public Box()
{
}
...
...
...
}
Box b1 = new Box();
Box b2 = new Box();
..
// so on
Box b100 = new Box();

but if you apply singleton pattern. it means you can create ONLY ONE object with it. In this pattern constructor is private it means you can't use like

Box b1 = new Box();
Box b2 = new Box(); // invalid ..

So singleton pattern is "Defining a Class with private constructor so that the code which is outside the class cannot create it".
following code creates a singleton class.

class Box{	
    private static Box instance ;	
    private Box()	
      {		...	
      }	
 public static Box getInstance()	
      {		
         if (instance == null)
 	     instance = new Singleton();
         return instance;	
      }		
 public void doSomething()	
     {		...		
     }
}

With the above defination you can access the object of class Box by

Box b = Box.getInstance();
b.doSomething();

But it is important to understand that where do we use singleton and we we not.
If we want a single gateway to common set of functionalities we use singleton class. like Logging, Configuration of Application, Server Client achitecture, Resource access, Global/shared values/variables ( company email, address etc.). common Data store acess point. If wisely used it saves lots of memory and increase performance.

How to determine the singleton behaviour of a Class.

In the simplest form,

If a entity in your application co-exists with different property values then it is not a candidate for singleton. for e.g. In school System , "Student" : Student-1 , Student-2 has a common property / behaviour but property values are different. (their name,age,address class are different).

If a Entity exists in System that is common and its property values are same,its a candidate for Singleton class. for e.g. Playground, Auditorium, School Notice Board. these are single instance object throughout the School system.

A in-depth analysis is required to get a list of classes that we can make singleton.

please refer http://www.oodesign.com/singleton-pattern.html[^] for more detail

Singleton pattern using baseclass

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