Field::HasAndBelongsToMany

The HasAndBelongsToMany field wraps a has_and_belongs_to_many association on your model. By default it adds a list of associated records to the show page and on edit and new pages it renders a checkbox list of available records.

How to add a HasAndBelongsToMany field

To add the basic HasAndBelongsToMany field to a repository, return it as part of the #fields method:

def fields
  [
    Field::HasAndBelongsToMany.new(:tags)
  ]
end

Search

Not searchable by default. The field isn’t backed by a real column, so enabling it needs a searchable lambda - see Search for columns in an associated table.

#collection_query

The chainable #collection_query method lets you control what records are available to pick from. It accepts a proc, which receives an ActiveRecord::Relation with all records for the associated repository.

Field::HasAndBelongsToMany.new(:tags)
  .collection_query(-> (query:) {
    query.some_scope
  })

The proc can accept the following keyword arguments:

1. context: The Uchi::Context we’re currently processing.
2. query: The ActiveRecord::Relation described above.

How to limit what records are returned

You can use #collection_query to limit what records are returned. The currently logged-in user is available as context.user, see Current user.

Field::HasAndBelongsToMany.new(:tags)
  .collection_query(-> (context:, query:) {
    query.where(id: context.user.tags)
  })

Show page

Associated records are listed in a scoped index table below the record’s other fields.

How to change titles in the checkbox list

The checkbox list and show page display the title of each associated record. For example, a Tag repository may use the name attribute as its title. To customize the title for a record, implement Repository#title, see repositories documentation for details.