Location services in React Native - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output of this React Native location request code?

Consider this React Native code snippet that requests location permission and fetches the current position. What will be the value of location after the code runs successfully?

React Native

import React, { useState, useEffect } from 'react';
import { View, Text, Button } from 'react-native';
import Geolocation from '@react-native-community/geolocation';

export default function LocationExample() {
  const [location, setLocation] = useState(null);

  const getLocation = () => {
    Geolocation.getCurrentPosition(
      pos => setLocation(pos.coords),
      err => setLocation({ error: err.message })
    );
  };

  useEffect(() => {
    getLocation();
  }, []);

  return (
    <View>
      <Text>{location ? JSON.stringify(location) : 'Loading...'}</Text>
    </View>
  );
}

A An error object with a message property always, because permission is denied by default

B A string 'Loading...' because location is never set

C Null, because useState was initialized with null and never updated

D An object with latitude and longitude properties representing the device's current position

💡 Hint

Think about what Geolocation.getCurrentPosition does when it succeeds.

The getCurrentPosition function calls the success callback with an object containing coords that has latitude and longitude. This updates the location state with these coordinates, so the UI shows them as a JSON string.

🧠 Conceptual

intermediate

Which permission is required to access location on Android in React Native?

To use location services in a React Native app on Android, which permission must be declared in the AndroidManifest.xml file?

A <uses-permission android:name="android.permission.INTERNET" />

B <uses-permission android:name="android.permission.CAMERA" />

C <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

D <uses-permission android:name="android.permission.READ_CONTACTS" />

💡 Hint

Location permission is about GPS or precise location.

The ACCESS_FINE_LOCATION permission allows the app to access precise location data from GPS or network sources. Other permissions like INTERNET or CAMERA are unrelated to location.

❓ lifecycle

advanced

What happens if you don't clear location watch in React Native?

In React Native, if you use Geolocation.watchPosition to track location changes but forget to clear the watch with Geolocation.clearWatch, what is the likely effect?

A The app will continue to consume battery and resources even when the component unmounts

B The location updates will stop automatically after 5 minutes

C The app will crash immediately due to memory leak

D Nothing happens; watchPosition cleans itself up automatically

💡 Hint

Think about what happens when background tasks are not stopped.

If you don't clear the watch, the location listener stays active, causing battery drain and unnecessary resource use. It does not stop automatically or crash the app immediately.

📝 Syntax

advanced

Which option correctly requests location permission using React Native Permissions library?

Given the React Native Permissions library, which code snippet correctly requests location permission on iOS?

A const result = await request(PERMISSIONS.IOS.LOCATION_WHEN_IN_USE);

B const result = await request('ios.permission.LOCATION_WHEN_IN_USE');

C const result = await Permissions.request('LOCATION_WHEN_IN_USE');

D const result = await requestPermission(PERMISSIONS.IOS.LOCATION_ALWAYS);

💡 Hint

Check the exact method and constant names from the library.

The correct usage is to import request and PERMISSIONS from the library and call request(PERMISSIONS.IOS.LOCATION_WHEN_IN_USE). Other options use wrong method names or string formats.

🔧 Debug

expert

Why does this React Native location code fail to update state?

This React Native code tries to get location but the UI never updates from 'Loading...'. What is the cause?

React Native

import React, { useState, useEffect } from 'react';
import { View, Text } from 'react-native';
import Geolocation from '@react-native-community/geolocation';

export default function App() {
  const [location, setLocation] = useState(null);

  useEffect(() => {
    Geolocation.getCurrentPosition(position => {
      setLocation(position.coords);
    });
  }, []);

  return (
    <View>
      <Text>{location ? JSON.stringify(location) : 'Loading...'}</Text>
    </View>
  );
}

A The Geolocation.getCurrentPosition callback is never called due to missing permissions

B The code assigns to the variable 'location' directly instead of using setLocation, so state does not update

C The useEffect hook is missing a dependency array, causing infinite re-renders

D The initial state should be an empty object, not null, to trigger rendering

💡 Hint

Remember how React state updates work.

React state variables must be updated using their setter functions. Direct assignment to the state variable does not trigger a re-render or update the UI.