The promise of simplicity does not match the reality. It's explained well here, this was linked in the article too: http://khanlou.com/2013/12/kvo-considered-h

The promise of simplicity does not match the reality. It's explained well here, this was linked in the article too: http://khanlou.com/2013/12/kvo-considered-harmful/ http://khanlou.com/2013/12/kvo-considered-harmful/