| --- | |
| id: common-mistakes | |
| title: Common Mistakes | |
| sidebar_label: Common Mistakes | |
| hide_title: true | |
| description: Common Mistakes | |
| --- | |
| import { InternalLinks } from '@site/src/components/InternalLinks' | |
| # Common Mistakes | |
| A somewhat common mistake is to write an <InternalLinks.InputSelectors text="input selector" /> that extracts a value or does some derivation, and a <InternalLinks.ResultFunction /> that just returns its result: | |
| ```ts | |
| // ❌ BROKEN: this will not memoize correctly, and does nothing useful! | |
| const brokenSelector = createSelector( | |
| [(state: RootState) => state.todos], | |
| todos => todos | |
| ) | |
| ``` | |
| Any <InternalLinks.ResultFunction /> that just returns its inputs is incorrect! The <InternalLinks.ResultFunction /> should always have the transformation logic. | |
| Similarly: | |
| ```ts | |
| // ❌ BROKEN: this will not memoize correctly! | |
| const brokenSelector = createSelector( | |
| [(state: RootState) => state], | |
| state => state.todos | |
| ) | |
| ``` | |