Difference between addModule and registerModule in TYPO3

Question

There are 2 functions in TYPO3 which seem to more or less do the same:

1. ExtensionManagementUtility::addModule

   /**
   * Adds a module (main or sub) to the backend interface
   * FOR USE IN ext_tables.php FILES
   

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2. ExtensionUtility::registerModule

   /**
   * Registers an Extbase module (main or sub) to the backend interface.
   * FOR USE IN ext_tables.php FILES
   

So, according to the comments, they basically do the same, but one registers and one adds and for one it's an Extbase module. I have seen examples for both online and seen TYPO3 extensions use one or the other methods.

Which of these methods should be use to create a TYPO3 backend-module and what is the difference?

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I can just use one or the other methods, but I would like to get some more guidance on these general things and what is the best practice for the future.

The obvious answer is probably, if you use Extbase, you use registerModule, if not, you use addModule. Ok, but then, why does the core do it this way in some cases and that way in the other?

Another obvious answer is that registerModule calls addModule.

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See also this comment.

Answer 1

With addModule you just add a new Module into the left navigation bar.

With registerModule you do some pre-configuration for extbase. Have a look into the code, all controller->action combinations will be registered globally. A vender will be set and please have a look at the very last line: It calls addModule from above.

Answer 2

Additionally, it looks like ExtensionUtility::registerModule() is used for modules based on Extbase, and ExtensionManagementUtility::addModule() otherwise (see BackendModuleApi)