BestRegistration

Table Of Contents

• Best Registration

Best Registration

You can register multiple registrations for a type T which allows you to resolve T[] and other collections of T. However, when resolving just one instance of T, StrongInject requires that there is a best registration for T, or it will error.

A best registration is defined as follows:

1. Any registration declared directly on a module/container is better than registrations declared on other modules and imported by the module/container.
2. If there is a single registration which is better than all other registrations it is considered the best registration. Else there is no best registration.

So for example, imagine there is a Container, and two modules, ModuleA and ModuleB.

If all three define a registration for SomeInterface, then the one defined on the container will always be the best registration.

If just ModuleA and ModuleB define a registration for SomeInterface then things will depend:

• If Container imports both modules, resolving SomeInterface will always result in an error (even if ModuleA imports ModuleB or vice versa).
• If Container imports ModuleA, and ModuleA imports ModuleB, then ModuleA's registration will be the best registration.
• If Container imports ModuleB, and ModuleB imports ModuleA, then ModuleB's registration will be the best registration.

To fix errors as a result of multiple registrations for a type, the simplest thing to do is to add a single best registration directly to the container. If the container already has multiple registrations for the type, then move those registrations to a separate module and import them.