React toggling Child components - SOLVED

I have a parent component that displays a card style child for each date. I want to be able to expand or contract just the day t hat is clicked on.

However when I put the toggle control in the parent, it toggles ALL the children, not just the instance I click on.

When I try to pass the show state from parent to child as props, I get an error :

Cannot update during an existing state transition (such as within render). Render methods should be a pure function of props and state.

I’ve searched but can only findn general tutorials that show one level of component being toggled.

PM me for solution, if lots interested will post here, otherwise too long to explain if nnno one is interested.