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--- |
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id: createSelectorCreator |
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title: createSelectorCreator |
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sidebar_label: createSelectorCreator |
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hide_title: true |
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description: 'createSelectorCreator' |
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--- |
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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 | |
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| :----------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | |
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| `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. | |
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| `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 | |
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| `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 | |
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| `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 | |
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| `options.memoize` | The memoize function that is used to memoize the `resultFunc` inside <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). since 5.0.0 | |
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| `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 | |
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| :-------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------- | |
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| `memoize` | The `memoize` function responsible for memoizing the `resultFunc` inside <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). | |
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| `...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 | |
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| :-------------------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | |
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| `MemoizeFunction` | The type of the memoize function that is used to memoize the `resultFunc` inside <InternalLinks.CreateSelector /> (e.g., `lruMemoize` or `weakMapMemoize`). | |
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| `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 |
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const customCreateSelector = createSelectorCreator({ |
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memoize: customMemoize, // Function to be used to memoize `resultFunc` |
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memoizeOptions: [memoizeOption1, memoizeOption2], // Options passed to `customMemoize` as the second argument onwards |
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argsMemoize: customArgsMemoize, // Function to be used to memoize the selector's arguments |
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argsMemoizeOptions: [argsMemoizeOption1, argsMemoizeOption2] // Options passed to `customArgsMemoize` as the second argument onwards |
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}) |
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const customSelector = customCreateSelector( |
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[inputSelector1, inputSelector2], |
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resultFunc // `resultFunc` will be passed as the first argument to `customMemoize` |
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) |
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customSelector( |
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...selectorArgs // Will be memoized by `customArgsMemoize` |
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) |
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``` |
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### Using `memoize` and `...memoizeOptions` |
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`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 |
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const customSelectorCreator = createSelectorCreator( |
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customMemoize, // Function to be used to memoize `resultFunc` |
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option1, // `option1` will be passed as second argument to `customMemoize` |
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option2, // `option2` will be passed as third argument to `customMemoize` |
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option3 // `option3` will be passed as fourth argument to `customMemoize` |
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) |
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const customSelector = customSelectorCreator( |
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[inputSelector1, inputSelector2], |
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resultFunc // `resultFunc` will be passed as first argument to `customMemoize` |
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) |
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``` |
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Internally `customSelector` calls the memoize function as follows: |
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```ts |
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customMemoize(resultFunc, option1, option2, option3) |
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``` |
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### Additional Examples |
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#### Customize `equalityCheck` for `lruMemoize` |
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```js |
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import { createSelectorCreator, lruMemoize } from 'reselect' |
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import isEqual from 'lodash.isequal' |
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// create a "selector creator" that uses lodash.isequal instead of === |
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const createDeepEqualSelector = createSelectorCreator(lruMemoize, isEqual) |
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// use the new "selector creator" to create a selector |
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const selectSum = createDeepEqualSelector( |
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[state => state.values.filter(val => val < 5)], |
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values => values.reduce((acc, val) => acc + val, 0) |
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) |
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``` |
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#### Use memoize function from Lodash for an unbounded cache |
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```js |
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import { createSelectorCreator } from 'reselect' |
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import memoize from 'lodash.memoize' |
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const hashFn = (...args) => |
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args.reduce((acc, val) => acc + '-' + JSON.stringify(val), '') |
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const customSelectorCreator = createSelectorCreator(memoize, hashFn) |
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const selector = customSelectorCreator( |
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[state => state.a, state => state.b], |
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(a, b) => a + b |
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) |
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``` |
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