Relation Field Conditions

Voxel's conditional logic can show or hide form fields based on text, numbers, dates, files, taxonomies, and switchers — but not post relation fields. This function fills that gap: show or hide any field based on whether a relation field has posts selected.

Overview

Once enabled, post relation fields become available as condition sources in Voxel's post type editor, with two new rules:

• Is empty — the relation has no posts selected
• Is not empty — the relation has at least one post selected

Conditions are evaluated live on the submission form (as the user picks or removes related posts) and re-checked server-side on submit.

Key Features

• Works with every relation configuration: has one, has many, belongs to one, belongs to many
• Works with custom relation keys and relation fields inside repeaters
• Live evaluation in the Create Post form — fields appear/disappear as selections change
• No configuration needed — enable and the rules appear in the post type editor

Setup Instructions

1. Navigate to Voxel Toolkit → Functions and enable Relation Field Conditions
2. Go to Voxel → Post Types and open the post type's Fields tab
3. Open any field's options and go to Conditional logic
4. Choose your post relation field as the condition source
5. Select Is empty or Is not empty
6. Save the post type

Use Cases

Conditional Detail Fields

Show a "Venue details" group only when no venue is related — hide it when the event links to an existing venue post.

Guided Submissions

Require either a relation selection or manual entry: reveal manual address fields only when the relation is empty.

Progressive Forms

Reveal follow-up fields once the user connects their listing to a parent post.

Troubleshooting

The relation field doesn't appear as a condition source

• Verify the function is enabled under Voxel Toolkit → Functions
• Reload the post type editor after enabling

Conditions don't react on the frontend

• Hard-refresh the submission page (the evaluator script may be cached)
• Check the browser console for JavaScript errors from other plugins