Group and count in Rails

You can do count on line_items which will return you an ordered hash of device_id and count.

@project.line_items.group(:device_id).count

hash of devise_id as key and associated records count

@project.line_items.group(:device_id).count

Just add a :select option:

@line_items = @project.line_items.all(
  :group  => "device_id",
  :select => "device_id, COUNT(*) as count"
)

Then each @line_item will have a count attribute.

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