When compiling, cmake failed during the linking process.
undefined reference to `vtable for MainWindow'
I received this error, after making one tiny mistake: I named my headerfile
Once renamed, everything should work fine.
Tiny hint: if you quickly want to copy the source displayed in this tutorial, but are as annoyed as I am about the line numbering which is copied as well, use the edit function of this site to access the (barebone) sourcecode.