use lazy state initialization to avoid eager deref calculation #95
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gmcnaughton
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Feb 18, 2021
| @@ -83,9 +83,9 @@ function useStoreDependency<Props, DepType>( | |||
| ): DepType { | |||
| enforceDispatcher(dispatcher); | |||
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| const [dependencyValue, setDependencyValue] = useState({ | |||
| const [dependencyValue, setDependencyValue] = useState(() => ({ | |||
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This is 💯 !
The only other tweak we could consider is literally moving the const newValue = { dependency: ... } up above here, then reusing newValue both as the initial state and where it is already used. That has the added benefit of skipping an extra eval of the deref in the opposite case (where we are initializing state for the first time)
gmcnaughton
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Feb 19, 2021
See HubSpot#95 Avoids duplicate deref calculations in `useStoreDependency`. Only calculate once; use this result to initialize state (if necessary) and as the next state. When the value changes, two deref calculations will still run: 1. the initial render/hook call 2. the re-render/hook call triggered by setting the new value in state
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gmcnaughton
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Mar 15, 2021
See HubSpot#95 Avoids duplicate deref calculations in `useStoreDependency`. Only calculate once; use this result to initialize state (if necessary) and as the next state. When the value changes, two deref calculations will still run: 1. the initial render/hook call 2. the re-render/hook call triggered by setting the new value in state
aem
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Mar 15, 2021
See #95 Avoids duplicate deref calculations in `useStoreDependency`. Only calculate once; use this result to initialize state (if necessary) and as the next state. When the value changes, two deref calculations will still run: 1. the initial render/hook call 2. the re-render/hook call triggered by setting the new value in state Co-authored-by: Gordon McNaughton <[email protected]>
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h/t @gmcnaughton for pointing out that we can optimize this hook with a lazy state init to avoid double-calculating the deref on every render, which can be meaningful for expensive derefs
TODOs
src/GeneralStore.jspackage.jsonCHANGELOG.mdis up to date