How do I Instantiate component as Singleton at registration?

Question

I can imagine this might be quite straight forward to do in Castle but I'm new to the technology and have been Googling for hours with no luck!

I have the following:

container.Register(
Component.For<MySpecialClass>().UsingFactoryMethod(
    () => new MySpecialClass()).LifeStyle.Singleton);

Now quite rightly this is being lazy-loaded, i.e. the lambda expression passed in to UsingFactoryMethod() isn't being executed until I actually ask Castle to Resolve me the instance of the class.

But I would like Castle to create the instance as soon as I have registered it. Is this possible?

Vacillating

Answer 1

You can just use the built it Startable facility like so:

container.AddFacility<StartableFacility>();
container.Register(Component.For<MySpecialClass>().LifeStyle.Singleton.Start());

You can read about it here

Invidious

Answer 2

For this simple case you could just register an existing instance:

var special = new MySpecialClass();
container.Register(Component.For<MySpecialClass>().Instance(special));

Ordure

Thank you! Here's what I ended up using - container.Register(Component.For<MySpecialClass>().Instance(new MySpecialClass())); – Vacillating

This does not look like the best approach since you are not leaving the instantiation to the container, and hence breaking the IoC pattern. – Optimal

@DavidPerlman Right, back when I wrote this answer, I think there wasn't such an easy way as the recent answer by MosheLevi describes. – Ordure

I find this a lot cleaner than the accepted answer. In my mind it shouldn't be about blindly following patterns. This makes it a lot easier for the next developer to figure out what's going on. And the instantiation and registration is still in one place. – Classless

Answer 3

The answer re using "Instance" may not always be feasible (if the class has layers of dependencies itself, it won't be easy to new it up). In that case, at least in Windsor 2.5, you could use this:

    public static void ForceCreationOfSingletons(this IWindsorContainer container)
    {
        var singletons =
            container.Kernel.GetAssignableHandlers(typeof (object))
                     .Where(h => h.ComponentModel.LifestyleType == LifestyleType.Singleton);

        foreach (var handler in singletons)
        {
            container.Resolve(handler.ComponentModel.Service);
        }
    }

    // usage container.ForceCreationOfSingletons();

Deedeeann