17 December 2024 Leave a comment Tech-Help
Encountering the “Possible unhandled promise rejection” error in React Native can be a common stumbling block for developers when dealing with asynchronous operations such as network requests. This error often indicates that a promise was rejected but the rejection was not handled properly. In this guide, we will explore effective strategies to address this issue using practical solutions.
Understanding the Error
The error message typically appears when a fetch operation fails, and the promise rejection is not caught and handled, leading to undefined data states. Here’s a simplified version of the code that might trigger this error:
return fetch(url)
.then(response => response.json())
.then(json => ({
city: json.name,
temperature: kelvinToF(json.main.temp),
description: _.capitalize(json.weather[0].description)
}))
.catch(error => console.log('There has been a problem with your fetch operation: ' + error.message));
Solution: Proper Error Handling
To effectively handle this error, ensure that your catch block either returns a value that can be managed by the calling function or throws an error that can be caught later in the chain. Here’s an updated approach:
return fetch(url)
.then(response => response.json())
.then(json => ({
city: json.name,
temperature: kelvinToF(json.main.temp),
description: _.capitalize(json.weather[0].description)
}))
.catch(error => {
console.log('There has been a problem with your fetch operation: ' + error.message);
throw error;
});
Then, in your React component, handle the error like this:
Api(region.latitude, region.longitude)
.then(data => {
console.log(data);
this.setState(data);
})
.catch(error => {
console.log("Api call error");
alert(error.message);
});
Additional Tips
- Ensure the API endpoint is accessible and not blocked by security settings. For iOS, consider adjusting the App Transport Security settings in Xcode.
- If running a local server, ensure it’s accessible from your device. Use the local IP address instead of localhost.
Integrating Automated Testing with Repeato
Once your promise handling is robust, consider enhancing your development workflow with automated testing. Repeato offers a no-code test automation tool for React Native mobile apps, allowing you to quickly create, run, and maintain tests. Its computer vision and AI capabilities provide a fast and efficient way to ensure your app handles network errors gracefully, without requiring extensive coding.
For more information on setting up automated tests with Repeato, visit our Getting Started guide and explore our documentation.
By following these guidelines, you’ll be better equipped to handle promise rejections in React Native and streamline your testing process with Repeato.
