Autogenerated context interface for strong-typed "service locator"
Peter
so I have been exploring an idea for packing dependencies into an
interface specialized for serving up dependencies.
The scenario I've been targeting with this is when I want to isolate
subclasses from changes in the superclass dependencies. So when
subclassing, in addition to any new dependencies the subclass
requires, we have to replicate dependencies from the superclass for
these to be resolved. An example first:
class SuperClass {
protected SuperClass(IServiceX x, IServiceY y) {}
}
class SubClass : SuperClass {
public SubClass(IServiceZ z, IServiceX x, IServiceY y) : base(x,y)
{}
}
With several subclasses and even classes implemented by third parties
using our libraries this becomes vulnerable to change. When we need to
add or change any of the existing dependencies in the superclass, this
will require changing all subclasses. So to alleviate this I introduce
a "dependency" interface:
class SuperClass {
public interface IDependencies {
IServiceX x {get;}
IServiceY y {get;}
}
protected SuperClass(IDependencies dependencies) {}
}
class SubClass : SuperClass {
public SubClass(IServiceZ z, IDependencies dependencies) : base
(dependencies) {}
}
Now with the dependency interface we can make changes to this
interface with no change to the subclasses (other than perhaps a
recompile). This interface now has a feel of being a service locator,
though it is strongly typed.
So far I would like to know if you Autofac folks have any take on this
from a DI perspective. My next take on this is to make using
dependency interfaces really easy by providing a means of
autogenerating implementations for such interfaces so instances can be
provided by an Autofac container.
Best regards
Peter
Nicholas Blumhardt
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Peter
www.castleproject.org/dynamicproxy) to generate the IDependency
implementations.
Should be easy to implement a registration source for it too.
If this still sounds as a good idea (I think so :) I would be happy to
contribute!
- Peter
On Nov 19, 1:38 am, Nicholas Blumhardt <nicholas.blumha...@gmail.com>
wrote:
>
> I've taken the same approach as you in the past - something like
> "IDependencies" to pass from subclasses to their base classes - but I'm
> always a bit wary of it outside the common case of controllers in MVC.
>
> When the framework is under my control :) I tend to want to get rid of the
> inheritance and turn the subclasses into Strategies - by tweaking the
> strategy interface you can usually eliminate the need for any base-class
> implementation.
>
> Looking forward to seeing where your investigation takes you - might be a
> good candidate for IRegistrationSource :)
>
> Nick
>
> > .
Nicholas Blumhardt
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Peter
yes, me sorry too for delay on my side :) I'm still on it though,
hoping to complete a package during the Holidays.
That said, I'm a bit unsure on what to name this contribution. I was
thinking of using "GeneratedFactoryServices", since the IDependency
interface could be viewed as a service containing a set of generated
factories.
It doesn't feel quite right though, would like something more
descriptive...
Another approach is to think of the interface as "a strongly typed
view on IContext"... GeneratedTypedContexts, perhaps?
As you can see, I could use some input on what to name the baby :) Any
input is appreciated!
- Peter
On Dec 10, 4:09 am, Nicholas Blumhardt <nicholas.blumha...@gmail.com>
wrote:
> Hi Peter,
>
> Still think it is a funky idea :)
>
> Sorry about the delay getting back to this - if you would like to package it
> up for AutofacContrib it would be welcome!
>
> Cheers,
> Nick
>
> 2009/11/30 Peter <plillev...@gmail.com>
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Peter
yes, me sorry too for late replies. I'm on the case though, it is not
forgotten :) I will prepare a package during the Holidays.
That said, I'm not quite certain what to call this contribution.
I've thought of calling it "GeneratedFactoryServices" since what the
"IDependency" interface really is could be viewed as a service
encapsulating one or more factories, all generated dynamically.
It could also be thought of as "a strongly typed view on the
IContext".... GeneratedTypedContexts perhaps?
Any thoughts on naming the baby would be great! :)
- Peter
On Dec 10, 4:09 am, Nicholas Blumhardt <nicholas.blumha...@gmail.com>
wrote:
> Hi Peter,
>
> Still think it is a funky idea :)
>
> Sorry about the delay getting back to this - if you would like to package it
> up for AutofacContrib it would be welcome!
>
> Cheers,
> Nick
>
> 2009/11/30 Peter <plillev...@gmail.com>
> > <autofac%2Bunsu...@googlegroups.com<autofac%252Bunsubscribe@googlegroup s.com>>
> > > > .
> > > > For more options, visit this group at
> > > >http://groups.google.com/group/autofac?hl=.
>
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Peter
a bit later than planned but I've been able to put some more effort
into the GeneratedTypedContext thingy now.
I have two approaches though, on how to register a GTC with a
container. Would love some input on which way is preferred:
1. Using a RegistrationSource
var builder = new ContainerBuilder();
builder.RegisterSource(new
GeneratedTypedContextRegistrationSource());
builder.RegisterType<GeneratedTypedContext<IServiceLocator>>();
var container = builder.Build();
var sl = container.Resolve<IServiceLocator>();
Here we uses a GeneratedTypedContext type to indicate that the
interface should be generated. When resolved for the actual interface,
the registration source
will be consulted and looks for a
GeneratedTypedContext<IServiceLocator> registration. If found, a proxy
for the interface is generated and returned for the registration.
A helper extension method RegisterGeneratedTypedContext will be
implemented to make registration easier.
2. Using "immediate" registration
var builder = new ContainerBuilder();
builder.RegisterGeneratedTypedContext<IServiceLocator>();
var container = builder.Build();
var sl = container.Resolve<IServiceLocator>();
This approach does not rely on a registration source. The extension
method generates the proxy and registers it with the container.
So, both approaches works fine, and is almost equal in use. I find 2)
a bit easier for the end-user though, since no registration source (or
module) is involved.
Perhaps there are other advantages to registration sources?
- Peter
On 23 Des 2009, 00:35, Nicholas Blumhardt
<nicholas.blumha...@gmail.com> wrote:
> GeneratedTypedContext sounds like a good working name to me.
>
> Cheers,
> Nick
>
> 2009/12/22 Peter <plillev...@gmail.com>
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>
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Nicholas Blumhardt
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