| --- |
| id: createSelectorCreator |
| title: createSelectorCreator |
| sidebar_label: createSelectorCreator |
| hide_title: true |
| description: 'createSelectorCreator' |
| --- |
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| import { InternalLinks } from '@site/src/components/InternalLinks' |
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| Accepts either a `memoize` function and `...memoizeOptions` rest parameter, or since 5.0.0 an `options` object containing a `memoize` function and creates a custom selector creator function. |
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| | Name | Description | |
| | :----------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | |
| | `options` | An options object containing the `memoize` function responsible for memoizing the `resultFunc` inside <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). It also provides additional options for customizing memoization. While the `memoize` property is mandatory, the rest are optional. | |
| | `options.argsMemoize?` | The optional memoize function that is used to memoize the arguments passed into the <InternalLinks.OutputSelector /> generated by <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). <br /> **`Default`** = `lruMemoize` before 5.0.0 and `weakMapMemoize` after | |
| | `options.argsMemoizeOptions?` | Optional configuration options for the `argsMemoize` function. These options are passed to the `argsMemoize` function as the second argument. <br /> since 5.0.0 | |
| | `options.inputStabilityCheck?` | Overrides the global input stability check for the selector. Possible values are: <br /> `once` - Run only the first time the selector is called. <br /> `always` - Run every time the selector is called. <br /> `never` - Never run the input stability check. <br /> **`Default`** = `'once'` <br /> since 5.0.0 | |
| | `options.memoize` | The memoize function that is used to memoize the `resultFunc` inside <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). since 5.0.0 | |
| | `options.memoizeOptions?` | Optional configuration options for the `memoize` function. These options are passed to the `memoize` function as the second argument. <br /> since 5.0.0 | |
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| | Name | Description | |
| | :-------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------- | |
| | `memoize` | The `memoize` function responsible for memoizing the `resultFunc` inside <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). | |
| | `...memoizeOptionsFromArgs` | Optional configuration options for the memoization function. These options are then passed to the memoize function as the second argument onwards. | |
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| A customized <InternalLinks.CreateSelector /> function. |
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| | Name | Description | |
| | :-------------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | |
| | `MemoizeFunction` | The type of the memoize function that is used to memoize the `resultFunc` inside <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). | |
| | `ArgsMemoizeFunction` | The type of the optional memoize function that is used to memoize the arguments passed into the <InternalLinks.OutputSelector /> generated by <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). If none is explicitly provided, `lruMemoize` will be used. | |
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| ```ts |
| const customCreateSelector = createSelectorCreator({ |
| memoize: customMemoize, // Function to be used to memoize `resultFunc` |
| memoizeOptions: [memoizeOption1, memoizeOption2], // Options passed to `customMemoize` as the second argument onwards |
| argsMemoize: customArgsMemoize, // Function to be used to memoize the selector's arguments |
| argsMemoizeOptions: [argsMemoizeOption1, argsMemoizeOption2] // Options passed to `customArgsMemoize` as the second argument onwards |
| }) |
| |
| const customSelector = customCreateSelector( |
| [inputSelector1, inputSelector2], |
| resultFunc // `resultFunc` will be passed as the first argument to `customMemoize` |
| ) |
| |
| customSelector( |
| ...selectorArgs // Will be memoized by `customArgsMemoize` |
| ) |
| ``` |
| |
| ### Using `memoize` and `...memoizeOptions` |
| |
| `createSelectorCreator` can be used to make a customized version of <InternalLinks.CreateSelector />. |
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| The `memoize` argument is a memoization function to replace the default configured memoizer (normally `weakMapMemoize`). |
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| The `...memoizeOptions` rest parameters are zero or more configuration options to be passed to `memoizeFunc`. The selectors `resultFunc` is passed as the first argument to `memoize` and the `memoizeOptions` are passed as the second argument onwards: |
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| ```ts |
| const customSelectorCreator = createSelectorCreator( |
| customMemoize, // Function to be used to memoize `resultFunc` |
| option1, // `option1` will be passed as second argument to `customMemoize` |
| option2, // `option2` will be passed as third argument to `customMemoize` |
| option3 // `option3` will be passed as fourth argument to `customMemoize` |
| ) |
| |
| const customSelector = customSelectorCreator( |
| [inputSelector1, inputSelector2], |
| resultFunc // `resultFunc` will be passed as first argument to `customMemoize` |
| ) |
| ``` |
| |
| Internally `customSelector` calls the memoize function as follows: |
| |
| ```ts |
| customMemoize(resultFunc, option1, option2, option3) |
| ``` |
| |
| ### Additional Examples |
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| #### Customize `equalityCheck` for `lruMemoize` |
| |
| ```js |
| import { createSelectorCreator, lruMemoize } from 'reselect' |
| import isEqual from 'lodash.isequal' |
| |
| // create a "selector creator" that uses lodash.isequal instead of === |
| const createDeepEqualSelector = createSelectorCreator(lruMemoize, isEqual) |
| |
| // use the new "selector creator" to create a selector |
| const selectSum = createDeepEqualSelector( |
| [state => state.values.filter(val => val < 5)], |
| values => values.reduce((acc, val) => acc + val, 0) |
| ) |
| ``` |
| |
| #### Use memoize function from Lodash for an unbounded cache |
| |
| ```js |
| import { createSelectorCreator } from 'reselect' |
| import memoize from 'lodash.memoize' |
| |
| const hashFn = (...args) => |
| args.reduce((acc, val) => acc + '-' + JSON.stringify(val), '') |
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| const customSelectorCreator = createSelectorCreator(memoize, hashFn) |
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| const selector = customSelectorCreator( |
| [state => state.a, state => state.b], |
| (a, b) => a + b |
| ) |
| ``` |
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