Rails 4 Inventory Application: database design and use of nested forms -

i built application , works nicely , quite simple: https://github.com/ornerymoose/devicecount . allows create new entry device specify count (ie, inventory amount) of device.

now though works, i've been told needs on 'per location' basis. ie, create entry , have 10 textfields (if there indeed 10 devices. amount never change nor devices change) devices, , each device text field, enter count device. choose location dropdown menu. when entry created, have:

-1 location

-10 devices listed, own count.

i'm struggling wrapping head around how design these models. should have entry , device model? separate count model?

would nested form best approach here?

any , input appreciated.

sounds you'd best inventory join model (with has_many :through):

#app/models/inventory.rb class inventory < activerecord::base    # id | device_id | location_id | qty | created_at | updated_at    belongs_to :device    belongs_to :location end  #app/models/device.rb class device < activerecord::base    has_many :inventories    has_many :locations, through: :inventories    accepts_nested_attributes_for :inventories end  #app/models/location.rb class location < activerecord::base    has_many :inventories    has_many :devices, through: :inventories end 

this allow set "quantity" of device each location (will have use accepts_nested_attributes_for):

#app/controllers/devices_controller.rb class devicescontroller < applicationcontroller     def new      @device = device.new      @locations = location.all    end     def create      @device = device.new device_params      @device.save    end     private     def device_params      params.require(:device).permit(inventories_attributes: [:qty])    end end  #app/views/devices/new.html.erb <%= form_for @device |f| %>   <%= f.text_field :name %>   <%= f.fields_for :inventories, location.all |i| %>      <%= i.number_field :qty %>   <% end %>   <%= f.submit %> <% end %> 

this allow create new device , have it's qty available through inventory.