I hope not to bother anyone. I don't have enough reputation points to comment and ask directly in that beautiful suggestion: https://stackoverflow.com/a/37403125/8261024 .
My additional question to that great solution is: what, if I want to detect only real changes? What I mean is: if the value of x.a changes, i will know. What, if the value of x.a was 42 and after the change it is 42 too, but I want only a real change of the value? I only want to know, if it changes to dolphin or fish or sth.
Maybe I am blind right know so I can't see the obvious.
Thanks.