Binding based on keys

[Michael Hart]

I'm using the latest ASP.NET MVC incarnation and trying to figure out
the cleanest way to hook Ninject up with the IControllerFactory
interface that you can specify to create controllers.

Basically, IControllerFactory has a CreateController method that is
called when instantiating controllers (of type IController) based on
the requested URL and is passed a string for the controller name (eg,
"home", "admin", etc). In my Ninject controller module I want to bind
a controller class to each controller name.

Now what I'm struggling with is a way to specify the string key/
controller-name at binding time. The method I've settled on for now is
to create a named context and then bind conditionally on that.

Here's what I mean:

public class NamedContext : StandardContext
{
public string Name { get; set; }

public NamedContext(IKernel kernel, Type service, string name)
: base(kernel, service)
{
Name = name;
}

public static Predicate<IContext> NameEquals(string name)
{
return c => c is NamedContext && ((NamedContext)c).Name
== name;
}
}

(in my Module.Load):

Bind
<
IController
>().To<HomeController>().OnlyIf(NamedContext.NameEquals("home"));

Bind
<
IController
>().To<UserController>().OnlyIf(NamedContext.NameEquals("user"));

(in my implementation of IControllerFactory):

public IController CreateController(RequestContext context,
string controllerName)
{
return kernel.Get<IController>(new NamedContext(Kernel,
typeof(IController), controllerName.ToLower()));
}

My main question is: is this the easiest way? Is there a way that I'm
missing to bind using string keys? All I could find is binding string
constants or passing strings to constructor arguments. I tried to
think about whether attributes could be used, but these can't be added
at runtime.

BTW - this doesn't just apply to string keys obviously - that
NamedContext could equally a generic "KeyContext" or similar with any
type as the key/name.

Cheers,

Michael

[Nate Kohari]

Michael:

You're doing some fun stuff with Ninject. :) I committed a new feature to the trunk that should help to solve your problem, and wrote a blog post about it: http://kohari.org/2008/03/13/context-variables-in-ninject/.

Let me know what you think, or if you have questions.


Thanks,
Nate

[Michael Hart]

Cheers Nate - that solution looks good - I've commented about it on
your blog post and just added a caveat regarding the controller name
case insensitivity.

Keep up the good work!