IoC (StructureMap) Best Practice

Question

By my (likely meager) understanding, doing this in the middle of a method in your controller / presenter is considered bad practice, since it creates a dependency between StructureMap and your presenter:

void Override() {
    ICommentForOverrideGetter comm = StructureMap.ObjectFactory.GetInstance<ICommentForOverrideGetter>();

since this dependancy should be injected into the presenter via the constructor, with your IoC container wiring it up. In this case though my code needs a fresh copy of ICommentForOverrideGetter every time this method runs. Is this an exception to the above best practice, or a case where I should re-think my architecture?

Answer 1

It is said that there is no problem in computer science which cannot be solved by one more level of indirection:

If you just don't want the dependency in your presenter, inject a factory interface, the real implementation could do new CommentForOverrideGetter or whatever.

Edit:

"I have no problem ignoring best practices when I think the complexity/benefit ratio is too high": Neither do I, but as I said in the comments, I don't like hard dependencies on IoC containers in code I want to unit test and presenters are such a case.

Depending on what your ICommentForOverrideGetter does, you could also use a simple CommentForOverrideGetter.CreateNew() but as you require a fresh instance per call, I'd suspect at least some kind of logic associated with the creation? Or is it a stateful "service"?

Answer 2

If you insist on doing service location in your method, you should at least inject the container into your controller, so that you can eliminate the static method call. Add a constructor parameter of type StructureMap.IContainer and store it in a field variable. StructureMap will inject the proper container. You can then call GetInstance() on that container, instead of ObjectFactory.

Answer 3

The answer I ended up going with, from Jeremy Miller, is to just inject the Func<ICommentGetter> into the presenter.