react-native-navigation/website/docs/docs-functional-components.mdx

---
id: functionalComponents
title: Using functional components as screens
sidebar_label: Using functional components
---

Both class components and functional components can be used as screens. There is no performance difference between the two. Deciding which type component to use boils down to user preference.

## Declaring static options
Static options are a great way to declare options close to where they are used. Declaring static options is done by first declaring the functional component, and then declaring the options on the function class.
```jsx
const MyScreen = (props) => {
  return (
      <View>
        <Text>Screen Component</Text>
      </View>
    );
};

MyScreen.options = {
  topBar: {
    background: {
      color: 'red'
    }
  }
}
```

## Listening to navigation events
Navigation events let you react to various events related to a specific component or the app its self. Read more about them [here](/react-native-navigation/api/events)

```jsx
import { useEffect } from 'react';
import Navigation from 'react-native-navigation';

function MyScreen(props) {
  useEffect(() => {
    const listener = {
      componentDidAppear: () => {
        console.log('RNN', `componentDidAppear`);
      },
      componentDidDisappear: () => {
        console.log('RNN', `componentDidDisappear`);
      }
    };
    // Register the listener to all events related to our component
    const unsubscribe = Navigation.events().registerComponentListener(listener, props.componentId);
    return () => {
      // Make sure to unregister the listener during cleanup
      unsubscribe.remove();
    };
  }, []);

  return (
      <View>
        <Text>Screen Component</Text>
      </View>
    );
}
```

In the example above, our listener is registered with the `componentId` passed in the second argument, and will receive only its related events.

:::tip
[underscopeio/react-native-navigation-hooks](https://github.com/underscopeio/react-native-navigation-hooks) is a wonderful library which greatly simplifies usage with hooks by introducing dedicated hooks for each event. The following example, which is taken from their docs, shows how to listen to all appear events and a particular screen's appear events:

```jsx
import { useNavigationComponentDidAppear } from 'react-native-navigation-hooks'

const ScreenComponent = ({ componentId }) => {
  // Global listener
  useNavigationComponentDidAppear(e => {
    console.log(`${e.componentName} (${e.componentId}) appeared`)
  })

  // Listen events only for this screen (componentId)
  useNavigationComponentDidAppear(e => {
    console.log(`${e.componentName} appeared`)
  }, componentId)

  return (
    <View>
      <Text>Screen Component</Text>
    </View>
  )
}
```
:::