Accessing Variables from other class

Development Programming & Scripting C++
1

Hi! As an example I have a variable in the GameInstance class let name it skillPoints and I need to modify it value using the PlayerState class. What is the code for casting? I need to add 1 skill points every time an event is triggered.
Thank you in advance!

2

MyGameInstance* instance = Cast<MyGameInstance*>(gameInstanceRef);

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3

I cannot understand. How can I access the GameInstance located skillPoints variable from the PlayerState?