A year of React but I still get render loops I don't know how to fix in situations like:
- A parent passes a onFinish prop to a child
- The child calls the onFinish function at some point
- onFinish changes something that causes a re-render
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(This becomes more complicated when intermediate components between that parent and child wrap onFinish into their own onFinish function that's passed down. Same problem but more steps makes it much more confusing.)
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It seems like the thing to do here is to useCallback every callback that's passed down? But the Hooks API Reference (reactjs.org/docs/hooks-ref) doesn't even talk about using it like that; it talks about it only in terms of optimization.
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It seems like useCallback roughly doubles the code size whenever I do it. Here's an actual screenshot of what it takes to satisfy the linter with and without useCallback. This is the actual example that prompted these tweets.
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Yes, I've found that in practice useCallback is necessary for most upward-control-flow situations. Agreed on the code size challenges! Usually, though, it doesn't make sense to re-render when callbacks change, so you can use weak callbacks: gist.github.com/andymatuschak/
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In this approach, the HTMLButtonElement (or whatever) gets assigned a callback that doesn't change over time, but that callback closes over an object (the ref) whose field (current) changes to the latest function literal whenever the hook's parent is dirtied.
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Interesting. I haven't tried this in code, but I can imagine situations where this would genuinely violate the dependencies that should be in place. E.g. if you conditionally define a callback to be one function body or another, then pass it down. Right?
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(I can't think of a reason that that would be necessary, but I'm just trying to imagine what the possible failure modes are here. If that's the worst one then maybe it's fine?)
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Hm, even in that case, it should be fine, since ref.current woudl be updated when your provided callback changed. Maybe I’d have to see the code?
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Sorry, I misunderstood. I think I'm still not really understanding. What happens if the function passed to useByrefCallback closes over some locals like props etc.? Won't it capture them as they were at definition time and hold those references forever?
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No: if the props change, the component calling useByrefCallback will rerender, which will create a new closure capturing the new props, which will then be stored in the hook’s inner ref.current.
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