Imagine you are writing library code to be used by 3rd party developers. Your code needs to be able to create service objects that these developers provide. However you don’t know which IoC container each of your callers will be using.
The Common Service Locator lets you cope with the above without forcing a given IoC on your users.
Within your library itself you may wish to register your own classes in the IoC, now it gets a lot harder as you need to choose a IoC for your own use that will not get in the way of your callers.
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