How do I use selectors in Recoil?

How do I use selectors in Recoil?

Selectors in Recoil are pure functions that can compute derived state or transform state from atoms. You can create a selector using the selector function.

Can you give me an example of a selector?

Sure! Here's a simple example:

import { selector } from 'recoil';
import { myAtom } from './atoms';

const mySelector = selector({
  key: 'mySelector',
  get: ({ get }) => {
    const myValue = get(myAtom);
    return myValue * 2; // Derived state
  },
});

How do I use this selector in a component?

You can use the useRecoilValue hook to access the selector in your component:

import { useRecoilValue } from 'recoil';
import { mySelector } from './selectors';

function MyComponent() {
  const value = useRecoilValue(mySelector);
  return <div>{value}</div>;
}

What if I want to use parameters in my selector?

You can create a parameterized selector by using the get function's second argument. Here's an example:

const myParameterizedSelector = selectorFamily({
  key: 'myParameterizedSelector',
  get: (param) => ({ get }) => {
    const myValue = get(myAtom);
    return myValue + param;
  },
});