views:

317

answers:

6

hey, hi i want put limit on object creation means a class can have at most suppose 4 objects not more than that how to achieve this?

+10  A: 

One approach is using an object factory that creates at most 4 instances. It's an interesting need... Would an object pool serve the same need?

marklai
+1 for both limited Factory and Object Pool.
LiraNuna
A Factory class with an object pool or cache would be the way to go here
Lars Mæhlum
+3  A: 

You can count the numbers of instances created by using a static class property to store the count. This can either be done in the class constructor or you can make use of a factory pattern. It is a bit difficult to answer this more precisely without knowing the target language.

Rouan van Dalen
+3  A: 

Try modifying the Singleton pattern. You can use a count variable. You'll need to keep the Constructor private to have control over the no. of instances.

Padmarag
That variant is called the MultiTon :)
mlaverd
@mlaverd - Agree :)
Padmarag
A: 

The simplest way to do this would be to have a class level attribute called "count", and in your constructor, just make sure that "count" isn't above a certain number.

//pseudocode
class foo
  static count = 0

  def constructor()
    if count < 4
      //create object
    else
      //there are too many!
Mike Trpcic
In this case, each object will have its own copy of count, which'll always be 0. The count variable needs to be static.
Padmarag
It's pseudo code, it doesn't need to be perfect.
Mike Trpcic
but at leat the essential should be right (as they are now)
peterchen
+1  A: 

One way to achieve is the Singleton Design pattern, Whenever we make a call to create an instance, check the count of the instance which are already created, if the instance count is already reached 4, then use the same instance for your application. TO have a count, Creat Static Int Counter = 0; and keep incrementing it to get the results.

harigm
A: 

This is short code snippest that will give the above result in c#

sealed class clsInstance
    {
        public static int count = 0;
        private static readonly clsInstance inst = new clsInstance();
        clsInstance()
        {

        }

        public static clsInstance Inst
        {
            get
            {
                if (count < 4)
                {

                    Console.WriteLine("object : " + count);
                    count++;
                    return inst;
                }
                return null;
            }
        }


    }

   class MainClass
   {
       public static void Main(String[] args)
       {
           clsInstance c1 = clsInstance.Inst;
           clsInstance c2 = clsInstance.Inst;
           clsInstance c3 = clsInstance.Inst;
           clsInstance c4 = clsInstance.Inst;
           Console.ReadLine();
           clsInstance c5 = clsInstance.Inst;
           Console.ReadLine();
       }
   }
Neo