Custom fields

User-defined properties that live outside the Book table (here in a property_values store) shown as extra columns. The model is untouched — the controller loads each PropertyDefinition and turns it into a CrudComponents::DynamicColumn, then passes the set as extra_columns: — to both crud_collection and the standalone crud_filter form. Each column carries a preload: (one query per page, no N+1), a typed filter: and a sort: — so Shelf (text), Weight (number range, in g), Signed (yes/no select) and Acquired (date range) filter with the control their type wants, not a plain text box. Try the inline filter row, the sort headers, and the sidebar form.

@books   = Book.all
@columns = []
@columns << CrudComponents::DynamicColumn.new(
  :price_usd,
  label: 'Price (USD)',
  as: :number,
  unit: '$',
  filter: ->(scope, geq:, leq:) { scope.where('price*1.1 >= ?', geq).where('price*1.1 <= ?', leq) },
  sort: ->(scope, dir) { scope.order(Arel.sql("(price*1.1) #{dir}")) }
) { |record| record.price * 1.1 }

@columns += PropertyDefinition.order(:id).map { |defn| defn.to_crud_column(Book) }

def to_crud_column(subject_model)
  definition = self
  CrudComponents::DynamicColumn.new(
    key.to_sym, label: label, as: renderer, unit: unit.presence,
    preload: ->(records) { definition.values_by_subject(subject_model, records) },  # one query/page
    filter:  definition.filter_for(subject_model),   # filters as the as: type (see below)
    sort:    ->(scope, dir) { definition.sort_scope(scope, subject_model, dir) }
  ) { |record, loaded| definition.cast(loaded[record.id]&.value) }                   # the value resolver
end

# Just a block — its control follows the column's as: flavor (number → range,
# date → range, boolean → yes/no, string → text):
def filter_for(subject_model)
  case flavor
  when 'number'  then ->(s, geq:, leq:) { ... }
  when 'boolean' then ->(s, eq:) { ... }
  when 'date'    then ->(s, geq:, leq:) { ... }
  else                ->(s, contains:) { ... }
  end
end

<%= crud_collection @books, fieldset: :compact, extra_columns: @columns %>
<%= crud_filter   Book, fieldset: :compact, extra_columns: @columns %>   <%# same dynamic columns in a standalone form %>

Read more: Dynamic columns  ·  Views