@jsulm
I absolutely concur, hence my:

[private] cannot access outside, unless you change that or put in friend

The point being to answer OP's

So If i understand correctly without modifying the code to test there is no way to test the connection.

They will have to make some change, which doubtless they were attempting to avoid. Just a heads-up.

@Yash001 if your issue is solved (aside for the fact that you need to read and incorporate several concepts, I guess), please don't forget to mark this post as solved. Thanks.

That was to whole error. As for code I have too much to post.

Anyhow I fixed it by creating a new header file, copying the contents from the original header file into the new one, deleting the original and renaming the new header file to the name of the original one.

Sorry mate but I see no point in continuing this conversation.

Some software developers agreed that they need the class “variant” for working with type-safe unions. They chose another useful programming interface. These software design decisions might influence other class libraries, don't they?

The Qt software library is using also a variant class for the support of the meta-object protocol, isn't it?