Cannot read property 'getBoundingClientRect' of undefined

I’m not sure how to reproduce it, but we just got a report for the above error on the line:

https://github.com/captivationsoftware/react-sticky/blob/master/src/sticky.js#L69

return this.refs.placeholder.getBoundingClientRect().top;

[dbarbalato]

No longer relevant with 6.x

[vcarl]

I see a few problems off the bat @gregoralbrecht, here’s a working sandbox https://codesandbox.io/s/9op7mw8v4y

One of the problems is what the warning is telling you. Stateless function components cannot be given refs, so when Sticky tries to get a ref of the rendered component to measure, it ends up with undefined, ultimately giving you the error on this issue. You can fix that by using a class component.

Another problem is that you’re not taking in the style argument from the Sticky callback, which is the mechanism used to actually make the component stay where it is. The callback needs to be ({ style }) => at the bare minimum to work, and your ActionBar component needs to pass the style prop to the actual DOM.