Multiproviders is another new concept introduced to the DI mechanism of Angular. They allow us to associate multiple providers with the same token. This can be quite useful if we're developing a third-party library that comes with some default implementations of different services, but you want to allow the users to extend it with custom ones. For instance, in the Angular's form module, multiproviders are exclusively used to declare multiple validations over a single control. We will explain this module in Chapter 7, Working with the Angular Router and Forms, and Chapter 8, Explaining Pipes and Communicating with RESTful Services.
Another sample of an applicable use case of multiproviders is what Angular uses for event management in its web workers implementation. Users create multiproviders for event management plugins. Each of the providers...
