How to Reload ASTextNode with NSTextAttachment Images in AsyncDisplayKit / Texture

Explore a solution for reloading ASTextNode images using NSTextAttachment in AsyncDisplayKit/Texture for iOS apps.
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Reloading ASTextNode with NSTextAttachment Images in AsyncDisplayKit / Texture

When building iOS applications using AsyncDisplayKit (now known as Texture), you might encounter a common scenario: displaying attributed text which contains images loaded via NSTextAttachment. After downloading these images asynchronously, you might find that despite making necessary calls to update your node layout, the ASTextNode that displays your text doesn’t get updated. In this post, we’ll look at how to effectively reload the ASTextNode to reflect changes in its content, especially when dealing with images.

The Problem

The core of the issue arises when attempting to replace the contents of an ASTextNode with updated images retrieved from asynchronous sources.

You've set the attributedText property of your ASTextNode using a custom NSTextAttachment.

After downloading the image, you've updated the attachment, yet the display does not reflect these changes despite utilizing methods like setNeedsLayout() and layoutIfNeeded().

To rectify this situation, we need a more structured approach in implementing our attachment handling and node updating logic.

Solution Overview

The solution to this problem can be broken down into a few key steps:

Create a Custom NSTextAttachment: Implement a subclass of NSTextAttachment that handles image URLs and dynamic bounds based on image aspect ratios.

Handle Image Downloading: Use a library like SDWebImage to download images asynchronously.

Update the ASTextNode: Once the image is downloaded, modify the existing attributed string of the ASTextNode to replace the old attachment with the new one containing the fetched image. Trigger a layout update to reflect these changes.

Step-by-Step Implementation

1. Custom NSTextAttachment

Here's how you can implement a custom subclass of NSTextAttachment:

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

2. Load Images Asynchronously

Utilize SDWebImageManager to fetch images and handle the download logic. This can be integrated into your didEnterPreloadState method.

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

3. Update ASTextNode's Attributed Text

Once the image download completes, you replace the old attachment in the attributed string and set the attributedText property. This approach ensures that the ASTextNode reflects the latest content.

Conclusion

By following the above steps, you can successfully manage and update images contained within ASTextNode using NSTextAttachment. This structured approach not only resolves the issue of displaying updated images but also leverages the capabilities of AsyncDisplayKit effectively.

Incorporating these techniques within your application will provide a seamless experience when dealing with attributed strings rich in content and images.

If you run into any issues implementing this solution, feel free to reach out for further clarification or assistance!