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Learn how to solve the common problem of API response data not reflecting in the DOM using Angular and Angular Material.
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This video is based on the question https://stackoverflow.com/q/74259724/ asked by the user 'Thanzeer Salim' ( https://stackoverflow.com/u/12056439/ ) and on the answer https://stackoverflow.com/a/74259821/ provided by the user 'Mr. Stash' ( https://stackoverflow.com/u/13625800/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the Issue of API Response Data Not Showing in DOM with Angular Material

When developing web applications using Angular and Angular Material, you might encounter a frustrating problem: API response data not displaying properly in the user interface (UI). Even when the console shows that the data is fetched successfully, the DOM fails to render the updated information. This post aims to break down the issue and offer a clear solution to this common problem.

Understanding the Problem

In the provided code, the ELEMENT_DATA variable is initially assigned hard-coded values. When an API call retrieves additional data and attempts to add it to ELEMENT_DATA, the UI does not update as expected. The main reason for this is Angular's change detection mechanism, which requires a proper approach to trigger UI updates after the data source changes.

Snapshot of the Existing Code

Here’s a simplified version of the existing component code that demonstrates this issue:

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

Despite adding new data, the UI does not refresh to reflect these additions.

The Solution

To ensure the UI can properly reflect the changes made to ELEMENT_DATA, you need to re-assign the dataSource variable after you update ELEMENT_DATA. This prompts Angular's change detection system to update the DOM accordingly.

Steps to Implement the Solution

Update your getInventoryTypes function: After adding new data to ELEMENT_DATA, we will explicitly assign the new array back to dataSource.

Use the spread operator: This reassigns dataSource with a new array reference which helps trigger change detection.

Here is the corrected code of the TestCompComponent:

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

Key Changes Explained

Reassignment: By setting this.dataSource = [...this.ELEMENT_DATA];, you create a new array reference. This signals Angular's change detection to update the UI.

Use of Promises: Ensure that your API service returns a promise or observable, so the data fetching is handled asynchronously.

Conclusion

Fixing the issue of API response data not showing in the DOM requires some understanding of Angular's data binding and change detection. By ensuring you reassign the dataSource variable after updating your data, you can make sure your UI reflects the latest data. This practice not only enhances performance but ensures a smoother user experience as well.

Final Words

Keep this solution in mind when working with Angular and Angular Material to avoid similar issues in the future. Happy coding!