Question

I am building up an Active Record Relation object in steps, allowing a user to filter a list of car parts by make and model of car:

parts = Part.where(:listed => (start_date..end_date))

unless filters[:make_id].nil? || filters[:make_id] == 0    
  parts = parts.joins(:car).
      where("cars.make_id = ?", filters[:make_id] ) 
end

unless filters[:model_id].nil? || filters[:model_id] == 0      
  parts = parts.joins(:car).
      where("cars.model_id = ?", filters[:model_id] ) 
end

etc...

This is repetitive, and I would like to pull this out into a method that takes ‘make_id’ and ‘model_id’ as parameters. One important feature to retain is that if a filter is nil (e.g. the user doesn’t specify the model) then parts for all models are returned.

I can’t figure out how to tackle this and I’m not sure what to Google. Can you help?

Answer 1

parts = Part.where(:listed => (start_date..end_date))

[:make_id, :model_id].each do |k|
  filters[k]
  .tap{|f| parts = parts.joins(:car).where("cars.#{k} = ?", f) unless f.to_i.zero?}
end