static question

Question

4.00/5 (2 votes)

See more:

Hey guys

I know that when an object is static only one of that object can exist at any given time. I also know that if a class is static I don't need to instantiate it to use it which is very useful :)

What i don't get is why is it useful to have a static variable inside of an instantiate-able class?

Example:

public class Foo
{
    public Foo(int Bar)
    {
        bar = Bar;
    }

    private static int bar;
    public static int Bar
    {
        get { return bar; }
        set { bar = value; }
    }
}

Thanks

Posted 12-Jan-10 1:07am

Harvey Saayman

Add a Solution

6 solutions

Solution 6

wrote:
What i don't get is why is it useful to have a static variable inside of an instantiate-able class?

Think about string.Empty. Empty is a public static field on class System.String. It is often used when you implement singleton design pattern.

Posted 12-Jan-10 6:30am

N a v a n e e t h

Solution 3

wrote:
why is it useful

IMO, its not (unless you want a counter of some sort).

Posted 12-Jan-10 2:02am

Abhinav S

Updated 12-Jan-10 2:04am

v2

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

benjymous · Accepted Answer · 2010-01-12T01:21:00

Solution 1

Generally, if you want multiple objects of the same type to share data. For example, you might have a static RootNode member, if all your objects need to refer to it - that way you only need to initialise it once for the whole class, rather than per-instance

Posted 12-Jan-10 1:21am

benjymous

CPallini · Accepted Answer · 2010-01-12T01:57:00

Solution 2

Every info that has to be shared by all the instances (or none of them) of the class could be a good candidate.
For instance if you want to count how many instances (pardon the pun) of the class were created.
:)

Posted 12-Jan-10 1:57am

CPallini

Updated 12-Jan-10 2:00am

v2

Rick Shaub · Accepted Answer · 2010-01-12T02:50:00

Solution 4

Another example is a Message class in which each instance has a unique ID that is the previously assigned ID + 1;

Posted 12-Jan-10 2:50am

Rick Shaub

Pete O'Hanlon · Accepted Answer · 2010-01-12T03:50:00

Thread safety can make heavy use of a static variable. If you are aiming to lock a section, it makes sense for the variable to be static so that you achieve the aim of locking based on one object. For instance:

private static readonly object _syncLock = new object();

public void CriticalProcess()
{
  lock(_syncObject)
  {
    // Do something critical here.
  }
}