1

Aside from being a bad, bad pattern in general, are there any ramifications of doing something like this to store an object as a property on the nancy module for the life of the request? Everything looks okay but not sure if this will result in any weirdness at scale... ie, cross-talk between requests, memory leaks, general shenanigans.

public class APIModule : NancyModule 
{
    public SomeConvolutedThing MyThing { get; set; }

    public APIModule()
    {
        Before += ctx => {
                try
                {
                    FormsAuthenticationTicket ticket = FormsAuthentication.Decrypt(HttpContext.Current.Request.Cookies["MyThing"].Value);
                    MyThing = JsonConvert.DeserializeObject<SomeConvolutedThing>(ticket.UserData);
                }
                catch
                {
                    MyThing = null;
                }             

            return null;
        };

        Get["/api/callit"] = parameters => {
         // check on status of MyThing before deciding what to return
        };
    }

}
tdubbs
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2 Answers2

1

You should be fine doing that, modules are constructed per request - there should be no need to use a before hook though, just stick that code in the start of your constructor as if you would when setting a property from a constructor parameter.

Steven Robbins
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1

As @StevenRobbins said, you can, but the question is - why? For the snipped you provided, using local variable in the constructor is just enough.

I can envision few other reasons to want to have this:

  1. Your route(s) use a private methods to do their work. Then a private readonly field will work (for the same reasons, each module is constructed per request). Or even better, make these private functions to accept myThing as parameter, and still use local var in ctor.

  2. You want to access this outside of the module - it's better to create your own class to hold this outside the module. Register it "per request" and have a beforerequest hook to fill the data, and inject into whatever other functionality needs it.

To elaborate on (2):

public interface IMyThingBag
{
    MyThing MyThing{get;set;}
}

public class MyBagFiller : IRequestStartup
{
    private readonly IMyThingBag _bag;
    public MyBagFiller(IMyThingBag bad)
    {
        _bad = bag;
    }

    public void Initialize(IPipelines pipelines, NancyContext context)
    {
        _bag.MyThing = new MyThing{.....};
    }
}

Now, anywhere in the chain (need to have the parts registered per request), you can inject the bag and use the thing :)

You can even inject it in the module if you need the data there.

Sunny Milenov
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  • Thank you Steven and Sunny. Chose Sunny's answer because, in fact, my scenario is very close to the one described (my example was very stripped down).... So if modules are constructed on every request, what's the point of the Before hook if you can do stuff directly in the ctor as long as it's "before" the route/endpoint definitions? Loving Nancy btw... just still trying to figure out its quirks. – tdubbs Apr 10 '15 at 17:36
  • @tdubbs: the before hook is for cross-cutting concerns (think logging, authorization, etc), which are not part of normal logic of the module. – Sunny Milenov Apr 15 '15 at 16:10