CODEWITHSUNDEEP
dependency-injectionioc-containersimple-injector
John
John

Reputation: 7059

IoC Container that can resolve types rather than merely instances

(EDIT: After writing this question I found at least one solution so this question is self-answered. It might still benefit from a pair of eyes that knows more about IoC containers than I do.)

I have a very special scenario that smells like it could make use of an IoC container, but a technical detail makes using using existing ones difficult.

The scenario is me toying with the following separation of user interface components (actually Blazor components, so let's call them Components) from model classes they then bind against (let's call them UiObjects).

All UiObjects have a default Component<U> (ie. where U : IUiObject) that can bind to them (think U = IUiCommand to GenericButtonComponent being a Component<IUiCommand>, etc.), but a user interface designer can override styling and logic by adding a new SpecialButtonComponent, also being a Component<UiCommand>, that can then also be used with IUiCommand. That special component could differ from the old one in html, css and even stateful logic, but it's always a drop-in replacement for the default one.

I know need some flexible way to choose the correct Component<U> for each U that is a IUiObject on the basis on all sorts of things (collecting from asseblies, xml configuration, clever mechanisms to prioritize types over each other, etc.).

You'd think that this is just what IoC containers are made for, but there's a catch: Blazor expects me to deliver types, not instances, that Blazor then itself creates. I need a

    Type componentType = container.ResolveType<IUiCommand>()

I've superficially looked at Autofac, Castle Windsor, Lamar, LightInject, SimpleInjector and only realized after writing this question that at least SimpleInjector can resolve a DependencyMetadata<IFoo> that contains the resolved type - no luck with any other framework so far though.

So I'll answer my own question here, but I'd still be curious which other IoC containers have that feature.

Upvotes: 0

Views: 193

Answers (1)

John
John

Reputation: 7059

Simple Injector can resolve a DependencyMetadata<IFoo> that contains the resolved type like this:

var implementationType =
    container.GetInstance<DependencyMetadata<IFoo>>()?.ImplementationType;

Upvotes: 1

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