Скачать или смотреть How to Make GraphQL Queries Nullable for Smooth Rendering in Next.js

Discover how to handle null values in GraphQL queries while using Next.js and WordPress. Learn about conditional rendering to fix TypeError issues.
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This video is based on the question https://stackoverflow.com/q/67908885/ asked by the user 'Ilir' ( https://stackoverflow.com/u/8502320/ ) and on the answer https://stackoverflow.com/a/67909348/ provided by the user 'xadm' ( https://stackoverflow.com/u/6124657/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Making GraphQL Queries Nullable in Next.js Applications

When developing applications using Next.js and a headless CMS like WordPress, developers often encounter issues while trying to fetch and display data with GraphQL. A common problem is the presence of nullable fields, particularly when posting data that may not always contain images or other expected properties. In this post, we will dissect this issue and provide you with a solution to effectively handle nullable fields in your GraphQL queries.

The Problem

Imagine you are building a blog with posts fetched from WordPress via GraphQL. Each post might contain optional data, such as a featuredImage. If you try to access the featuredImage property in a post that doesn't have an image, you might run into a TypeError: Cannot read property 'node' of null. This error prevents your application from rendering the page, which is not a great user experience.

Here’s an example of a problematic query in a Next.js application:

[[See Video to Reveal this Text or Code Snippet]]

In the above code, when post.featuredImage is null, the Image component tries to read node.sourceUrl, leading to an error.

The Solution: Conditional Rendering

The good news is that the problem isn’t with your query or types. GraphQL supports nullable types, which means it's completely fine for some fields to be null in the data returned. The key to resolving this issue lies in adjusting your rendering logic to gracefully handle cases where data might be absent.

Implementing Conditional Rendering

We will use conditional rendering to check if featuredImage exists before attempting to access its properties. This is how you can modify your rendering function:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Conditional Rendering

Logical AND Operator (&&): In the line {post.featuredImage && <Image ... />}, the && operator first checks if post.featuredImage is truthy (i.e., not null or undefined).

If featuredImage exists, the <Image> component renders correctly with the provided source URL.

If featuredImage does not exist, nothing is rendered in its place, allowing the page to display without issues.

Benefits of This Approach

Robustness: Your app will not crash due to null values.

Improved User Experience: Users can still view posts even if certain data points, like featuredImage, are missing.

Development Flexibility: This style supports flexible content structures, allowing for richer media experiences.

Conclusion

By incorporating conditional rendering into your Next.js application, you can ensure that nullable GraphQL data is handled gracefully, preventing unwanted errors and improving the overall user experience. As web development continues to prioritize flexibility, techniques like these will become standard practice, allowing developers to build more resilient applications.

Always remember, handling nullable fields in your data is an integral skill that enhances the robustness of your application and maintains a smooth experience for your users.