sap.ui.core.mvc.ControllerExtension does not allow multiple extend calls

[dfenerski]

OpenUI5 version: latest

Browser/version (+device/version): CR latest

URL (minimal example if possible):

ce = sap.ui.core.mvc.ControllerExtension.extend('my.ns', {test: function(){console.error('bla')}})
ce.extend // undefined

compared to

b = sap.m.Button.extend('my.ns', {test: function(){console.error('foo')}})
b.extend // allows subclasses 

What is the expected result?
ControllerExtension does not allow inheritance & reuse of ControllerExtensions is therefore limited e.g I can't have the same base extension in a lib and 2 specialized extensions, inheriting the base one's functionality in apps.

[tsanislavgatev]

I've created an internal incident 2370143666. The status of the issue will be updated here in GitHub.

[Thodd]

Hi @dfenerski,

I discussed this topic with the responsible colleagues and the behavior you're seeing is actually intentional.

Extending a ControllerExtension by class inheritance conflicts with the override mechanism provided by the extensions.
So basically, multiple inheritance layers are not supported as of now.
On a technical level, the second subclassing is prevented by making the extension class final: true.
The reasoning is that a ControllerExtension must only be "extended" via the overrides, where final flags and the privacy setting (public: true or public: false) can be correctly validated.

See also here for the override functionality:
https://ui5.sap.com/#/api/sap.ui.core.mvc.ControllerExtension%23methods/sap.ui.core.mvc.ControllerExtension.override

To be fair the documentation is rather lacking and there already are two internal backlog item for the team to enhance the documentation:

• CPOUI5FRAMEWORK-117
• CPOUI5FRAMEWORK-150

Hope that helps you out a bit.

Best regards,

Thorsten