Troubleshooting

Common issues and their solutions when working with Plutonium.

Resource Class Detection

"Failed to determine the resource class" Error

Error messages:

NameError: Failed to determine the resource class for MyPortal::PostMetadataController.
Rails singularized "PostMetadata" to "PostMetadatum", but "PostMetadata" exists.
Add an inflection rule to config/initializers/inflections.rb.

or:

NameError: Failed to determine the resource class.
Please call `controller_for(MyResource)` in MyPortal::MyResourceController.

Cause: Plutonium infers the resource class from the controller name by singularizing it. For resources with names that don't follow standard Rails pluralization (like PostMetadata), Rails may singularize incorrectly (PostMetadata → PostMetadatum). Plutonium detects this and provides a helpful error message.

Solution: Add a custom inflection rule in config/initializers/inflections.rb:

ActiveSupport::Inflector.inflections(:en) do |inflect|
  # Preserve "Metadata" when singularizing (e.g., PostMetadata stays PostMetadata)
  inflect.singular(/(M)etadata$/i, '\1etadata')
end

This ensures Rails correctly handles the singularization throughout your application, including:

• Controller to model resolution
• Route generation
• Association lookups

Alternative: If you can't modify inflections, explicitly set the resource class in your controller:

class MyPortal::PostMetadataController < MyPortal::ResourceController
  controller_for Blogging::PostMetadata
end

Common Words Needing Inflection Rules

Word	Without Rule	With Rule	Inflection
Metadata	PostMetadatum	PostMetadata	inflect.singular(/(M)etadata$/i, '\1etadata')
Media	PostMedium	PostMedia	inflect.singular(/(M)edia$/i, '\1edia')
Data	PostDatum	PostData	inflect.singular(/(D)ata$/i, '\1ata')
Criteria	SearchCriterium	SearchCriteria	inflect.singular(/(C)riteria$/i, '\1riteria')

URL Generation

Wrong URLs for Nested Resources

Symptom: URLs for nested resources include unexpected IDs or route to the wrong path.

Cause: Rails "param recall" fills in missing parameters from the current request when generating URLs. This can cause issues when both top-level and nested routes exist for the same resource.

Solution: Plutonium handles this automatically by using named route helpers for nested resources. Ensure you're using resource_url_for instead of url_for:

# Good - uses Plutonium's smart URL generation
resource_url_for(@comment, parent: @post)

# May have issues with param recall
url_for(controller: 'comments', action: 'show', id: @comment.id)

Need More Help?

If you encounter an issue not covered here, please open an issue on GitHub.

Related

• Nested resources
• Adding resources
• Reference › Behavior › Controllers — controller_for, resource_url_for, current_parent
• Reference › Tenancy › Nested resources — nested URL generation
• Rails Inflections