Having initialization code certain to run only once

Question

I have this static class in an ASP.NET MVC project:

  public static class Setup
  {
    private static bool _intialized = false;

    public static void Initialize(IWindsorContainer Container)
    {
      //Check if it has already run
      if (_intialized)
      { return; }

      var connectionString = config.ConnectionStrings["ccsMongo"].ConnectionString;
      var dbName = config.AppSettings["ccsMongoDb"];

      //Initialization code here.
      Container.Register(
          Component.For<IOrgRepos>().ImplementedBy<OrgRepos>()
            .DependsOn(new { ConnectionString = connectionString, DatabaseName = dbName}),
          Component.For<IIndividualRepos>().ImplementedBy<IndividualRepos>()
            .DependsOn(new { ConnectionString = connectionString, DatabaseName = dbName}),
          Component.For<IScoreboardRepos>().ImplementedBy<ScoreboardRepos>()
            .DependsOn(new { ConnectionString = connectionString, DatabaseName = dbName})
        );

      //Mark as run
      _intialized = true;
    }
  }

I then include a call to it in my Application_Start. The intent is to be sure that it will never run more than once.

Is there a better way to create a function that can't be run more than once in the the application lifetime?
Am I being paranoid? I could just put a call to the initialization code into my Application_Start and forget about the "run only once" guard code.

I would be delighted to get any feedback.

Is there any way that you can use a static constructor? Right now the parameter gets in your way. Where does the IWindsorContainer come from, and why can it be called multiple times, and yet should be "initialized" only once? — Leonid
– Leonid, Commented Feb 25, 2012 at 21:22

Pete · Accepted Answer · 2014-05-07 07:11:54Z

I would not place logic to prevent the code from executing multiple times.

The function itself does not operate on static data, but data passed as arguments. This makes it a very reusable function. It is simply a function that can configure a Windor container, but the function doesn't care about which container it is.

The application does however care. The application desires to only have one container. Thus it is the application's responsibility to only create one container, and calling the function once for that container.

Lets say you later want to create an automated test verifying that this function initializes the container correctly. That test would create a new container, call this function with that container as argument, and then operate on the container, verifying its state.

If this function by itself prevents from being initialized more than once, you would be at a serious disadvantage in creating such tests.

You could however do something else. If the function could examine the state of the passed container, it could determine if that container has already been configured. The function would then be able to make sure that a specific instance of a container is only configured once. But personally, I wouldn't bother in this particular case.

Jesse C. Slicer · Accepted Answer · 2012-01-03 01:50:40Z

This could execute more than once pretty easily if called on multiple threads at the same time. This should make it a bit more foolproof:

  public static class Setup
  {
    private static readonly object _locker = new object();
    private static bool _intialized = false;

    public static void Initialize(IWindsorContainer Container)
    {
      lock (_locker)
      {
        //Check if it has already run
        if (_intialized)
        { return; }

        var connectionString = config.ConnectionStrings["ccsMongo"].ConnectionString;
        var dbName = config.AppSettings["ccsMongoDb"];

        //Initialization code here.
        Container.Register(
            Component.For<IOrgRepos>().ImplementedBy<OrgRepos>()
              .DependsOn(new { ConnectionString = connectionString, DatabaseName = dbName}),
            Component.For<IIndividualRepos>().ImplementedBy<IndividualRepos>()
              .DependsOn(new { ConnectionString = connectionString, DatabaseName = dbName}),
            Component.For<IScoreboardRepos>().ImplementedBy<ScoreboardRepos>()
              .DependsOn(new { ConnectionString = connectionString, DatabaseName = dbName})
          );

        //Mark as run
        _intialized = true;
      }
    }
  }

Mike Nakis · Accepted Answer · 2012-01-03 09:15:50Z

1

Jesse's answer is good. My personal preference would be to put it inside Application_Start. I would do this because this code does not have any state, and since it has no state, it does not deserve to be a class. (The only state it has is trying to make sure it does not get invoked twice, so that does not count.)

answered Jan 3, 2012 at 9:15

Mike Nakis

2,0011 gold badge13 silver badges15 bronze badges

\$\begingroup\$ That is interesting; you hold it that state is the only justification for a class? \$\endgroup\$

Matthew Nichols
– Matthew Nichols

2013-08-10 01:35:25 +00:00
Commented Aug 10, 2013 at 1:35
\$\begingroup\$ In my book, it is by far the major justification. I usually take lack of state as an indication that whatever it is that I am looking at is probably suitable as part of something else. But there are no absolutes in this world. There certainly exist different considerations which might be taken into account in making the decision of whether something deserves to be a class or not. For example, you may turn something into a class despite the fact that it has no state, if you foresee that some of its functionality may, through inheritance, be reused and some of it altered by an inheritor. \$\endgroup\$

Mike Nakis
– Mike Nakis

2013-08-10 21:17:34 +00:00
Commented Aug 10, 2013 at 21:17

Add a comment |

Stack Exchange Network

Having initialization code certain to run only once

3 Answers 3

You must log in to answer this question.

Hot Network Questions

Having initialization code certain to run only once

3 Answers 3

You must log in to answer this question.

Related

Hot Network Questions