Conditionally Create Instance

[Steven Smith]

I'm looking to pass back a Cached implementation of an object to all
requests for the type, except for the request made by the Cached
implementation itself - that should pull back the implementation that
fetches the data from its source.

I've tried this:

x.For<IAlbumRepository>().Use<CachedAlbumRepository>();

x.For<CachedAlbumRepository>().Use<CachedAlbumRepository>().Ctor<IAlbumRepository>().Is
<EfAlbumRepository>();

It fails with a "No default constructore defined" exception.

I started down this path:

x.For<IAlbumRepository>().Add(
c =>
{
if ( %%TheRequestingType%% is
CachedAlbumRepository)
{
return new
CachedAlbumRepository(new EfAlbumRepository());
}
return new EfAlbumRepository();
});

but I can't seem to figure out how to write a conditional that is
based on the type doing the requesting.

Any advice?

Thanks,
Steve

--
Steve Smith
http://SteveSmithBlog.com/
http://twitter.com/ardalis

[Kyle Malloy]

All you would need is the following configuration. To achieve the decorator pattern.

x.For<IAlbumRepository>().Use<CachedAlbumRepository>()

 .Ctor<IAlbumRepository>().Is<EfAlbumRepository>();

Hopes this helps,

~Kyle

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[Steven Smith]

Awesome, thanks! That works perfectly.

Steve

[Nitin Ved]

I had a question about this. If EfAlbumRepository requires a parameter for its constructor. How would I configure it ?

 

Adding the extra line for concrete class does not seem to work. I still get error Missing requested Instance property "fooInput" for InstanceKey "81f439f7-2d00-46a3-bc6a-53c0fe2bc77a"  when requesting an instance for IAlbumRepository from ObjectFactory.

 

x.For<IAlbumRepository>().Use<CachedAlbumRepository>().Ctor<IAlbumRepository>().Is<EfAlbumRepository>();

For<EfAlbumRepository>().Use<EfAlbumRepository>().Ctor<FooType>("fooInput").Is(foobar);

Steve

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[Scott]

If I had a generic repository setup:

IRepository<T>, Repository<T>, CachedRepository<T>

How would I set up StructureMap in the same way? I can't use Ctor<> because it doesn't have a Ctor(type theType) overload, and you can't have "Ctor<IRepository<>>" since that produces a compiler error.

Thanks!