---
id: screen-lifecycle
title: Screen Lifecycle
sidebar_label: Screen Lifecycle
---

Any React Component registered with react-native-navigation is enhanced with two additional lifecycle events:

* `componentDidAppear` - called each time a component is revealed to the user
* `componentDidDisappear` - called each time a component is hidden from user's view **as a result of being detached from hierarchy**

These methods compliment React's liefcycle methods:

* `componentDidMount` - called once, when a component is attached to hierarchy **for the first time**
* `componentWillUnmount` - called once, when a component is destroyed

### Mounting
These methods are called in the following order when a component is created and attached to hierarchy.

* constructor()
* render()
* componentDidMount()
* componentDidAppear()

### Unmounting
These methods are called when a component is being removed from hierarchy

* componentDidDisappear()
* componentWillUnmount()

### Modal

When a modal is displayed, depending on the [modalPresentationStyle](options-root.mdx#modalpresentationstyle), content behind it might be detached from hierarchy. This affects the visibility events which are emitted to the content behind the modal.

When Modals with `pageSheet` or `overCurrentContext` modalPresentationStyle are displayed, previous content is still visible to the user. Thus `componentDidDisappear` event is **not** emitted.

Same is applied when a modal is dismissed. If it was originally presented with `pageSheet` or `overCurrentContext` modalPresentationStyle, when that modal is then dismissed, the previous context won't receive a `componentDidAppear` event.

### Overlay
These methods are called in the following order when a component is displayed as an Overlay:

* constructor()
* render()
* componentDidMount()
* componentDidAppear()

:::note
Content displayed behind an Overlay does not receive the `componentDidDisappear`, since it's still visible to user and attached to the hierarchy.
:::