This demo UI Extension for GraphCMS can be used to compute and store custom fields in your model. It uses the Mustache templating engine to compute the titles.
Deploy the code to Vercel, or run locally. Then install this extension on GraphCMS as a UI extension using the URL to your index page as the URL (following this guide).
For testing purposes, you can also use the Github Pages url for this repository: https://gijshendrix.github.io/uix-computed-field/
Install the extension through the UI Extensions page in your project settings. Proceed to add a Computed Field to one of your models. In the field settings, specify the Computed field template using Mustache template (see reference below for syntax). Values from other fields are accessed by their apiID (so the value of a field called years would be rendered by using the template {{years}}'. For reference fields, usually only the title is accessible. This can be used in the template by using the following syntax: {{<apiid_of_reference_field>.<name_of_title_field_in_reference>}} in case the reference is of type "to-one". For "to-many" references, it's possible to use this syntax from Mustache: {{#<apiid_of_reference_field>.connect}} {{<name_of_title_field_in_reference>}} {{/<apiid_of_reference_field>.connect}} where connect is an internal name that must be used exactly as is.