expo-permissions
- React Native course
- Intermediate
- Lesson 107/116
- 5 min
Learn to ask for permissions with expo-permissions.
What is expo-permissions?
expo-permissions is Expo's module for asking permissions. Permissions.askAsync(Permissions.CAMERA) requests a permission; the result is an object with a status field. status has three values: 'granted', 'denied', 'undetermined'.
Usage: import with import * as Permissions from 'expo-permissions', then request with await Permissions.askAsync(Permissions.CAMERA). askAsync returns a promise; that is why it is called with async/await. getAsync reads the current state without asking. The first request shows a system dialog; later calls do not show it again. In Expo projects this module is included by default.
askAsync
Permissions.askAsync(permissionType) requests a permission. On the first call it shows a system dialog; later calls return the remembered result. It returns a promise; you wait with await.
The returned object is shaped like { status, expires, permissions }. The most used field is status. Example: const { status } = await Permissions.askAsync(Permissions.CAMERA). If status === 'granted' the camera can open; otherwise the user should be guided. The expires field tells when the permission expires on iOS; on Android it is usually 'never'. This detail can be ignored in most cases.
Practice Write requestCameraPermission
Write a requestCameraPermission function. Make it async. Call Permissions.askAsync(Permissions.CAMERA) with await; take status from the result and return it.
Starter code
// Write the requestCameraPermission function
// Ask CAMERA permission with Permissions.askAsync; give back the statusSample solution
async function requestCameraPermission() {
const { status } = await Permissions.askAsync(Permissions.CAMERA);
return status;
}Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match each method to its role
| Term | Meaning |
|---|---|
askAsync |
Asks permission |
getAsync |
Reads current state |
status |
Result field |
Permissions.CAMERA |
Camera permission |
2 Permissions import
import * as ____ from 'expo-permissions';import * as Permissions from 'expo-permissions';Explanation: Permissions is imported from expo-permissions.
3 What does askAsync return?
const { status } = await Permissions.askAsync(Permissions.CAMERA);- A string
- A number
- An object Correct answer
- An array
Explanation: askAsync returns an object with a status field.