Add Support for Custom Resolution

[spasarto]

I would like to discuss the possibility of adding the ability to customize type resolution. As of right now, the current implementation of Resolve looks like this:

    public object GetService(Type serviceType)
    {
        try
        {
            return _container.Resolve(serviceType);
        }
        catch  { /* Ignore */}

        return null;
   }

This works for simple cases, but it doesn't allow us to pass in additional values into the resolution - names or resolver overrides. It may also be nice to respond to resolution errors. For reference, here is the current Unity Resolve method:

 public object Resolve(Type typeToBuild, string nameToBuild, params ResolverOverride[] resolverOverrides);

One possibility is to add support for IOptions<ResolutionOptions>, where ResolutionOptionslooks like this:

 public class ResolutionOptions
 {
      public Fun<IUnityContainer, Type, object> Resolve {get;set;}
 }

[ENikS]

You have several options here:

• Add factory to the ServiceCollection or Unity registration to create type manually
• Register type with IUnityContainer.RegisterType providing required injection members
• Resolve IUnityContainer and use IUnityContainer.Resolve with appropriate overrides

[spasarto]

Thanks for the reply.

The first two cases address registration overrides, which is a different scenario. The third option requires me to do the resolution, which doesn't work when code I don't control is performing the resolution.

For example, let's say I have a web project, and I register my types normally. However for certain web requests, I want to resolve a different set of dependencies (ie, dryrun/beta implementations/regional cases, etc). Because I don't have access to type resolution, I am stuck resolving whatever I registered. This pushes the burden to all of my implementations to know if they need to handle this other case. I would prefer to pass in a ResolverOverride to unity's resolution that informs the container to resolve the second set of dependencies, when appropriate.

Hopefully that better explains the need for this customization.

[ENikS]

It could be simply done by creating either IBuildPlanCreatorPolicy or IBuildPlanPolicy factories.

These will have access to resolver overrides you want to pass so you could customize resolution to your liking.

[spasarto]

Fair point. We can close this issue in favor of those suggestions.