[Solved] Undefined reference to CustomScene()::CreateScene()

[Solution] : You have to add reference to files in the cMakeLists file in the
“# add cross-platforms source files and header files” section

As the title suggests I am getting an error:

…/…/…/…/…/…/Classes/AppDelegate.cpp:111: error: undefined reference to ‘CustomScene::createScene()’

,when building to android. It compiles and runs how I would expect when using Visual Studio, but when I try to test on android studio I get this error. It previously worked in both places with the helloWorld file, which I replaced with my custom one.