Passing keys to children in React.js

I am running through a react tutorial on tutsplus that is a bit old, and the code doesn’t work as it was originally written. I actually am totally ok with this as it forces me to learn more independently, however I have spent a while on a bug that I just can’t figure out. The bug consists of not being able to pass on an objects key, which prevents my program from updating the state of the correct object.