Should useDerivedValue cause a rerender?

Description

If I format a date on the ui thread like so…

const date = useDerivedValue(() => {
    const d = interpolate(translation.x.value, [0, width], [MIN, MAX]);
    return formatDateOnUI(d);
});

return <Text>{date}</Text>

In this example date will update (can check by logging d before return), however it will not update the UI… I can hack around this by calling some setState with runOnJS and that triggers a re-render but of course affects fps on the JS thread

Package versions

• React: 16.13.1
• React Native: ~0.63.3
• React Native Reanimated: 2.0.0-rc.0

[karol-bisztyga]

you only want to ensure it runs only once

I think that does not break a thing, however, it would be inefficient as it overwrites collections on both, js and the native side.

[jakub-gonet]

@anastely, you can add it wherever you want, you only want to ensure it runs only once. index.js or App.js or any standalone configuration file that is included there is fine. Using that in a component file (outside of component definition) is also fine but you may prefer a more “global” place to keep your configs in.