Question

it’s possible make a dropdown menu where menu’s fields are datas that comes from several mysql tables? I explain better: suppose that I’ve two models “Hardwares” and “Brands” and suppose that:

class Hardware < ActiveRecord::Base
belongs_to :brand
end

and

class Brand < ActiveRecord::Base
has_many :hardwares
end

and suppose that Hardware migration is:

class Hardwares < ActiveRecord::Migration

def self.up
  create_table "hardwares" do |t|
    t.column "model", :string
    t.column "id", :integer
     t.column "brand_id", :integer
  end
end

def self.down
  drop_table "hardwares"
end

I’d want that each dropdown menu element is something like that:

@hw=Hardwares.find(params[:id])

[@hw.brand.name,@hw.model]   <- Dropdown menu's element

In witch way can I do this?
Thank you all in advance

Answer 1

As I understand it, you want to associate Hardware to a Project but when listing the Hardware you want to include the brand name to avoid a list of model numbers.

Update: Define the following in your Hardware model:

def model_with_brand_name
  "#{self.brand.name} #{self.model}"
end

Unfortunately, the Rails API docs don’t allow linking directly to methods but what you want is collection_select.

In a form, you can create a select element menu using the following method:

<%= collection_select :project_id, Hardware.all, :id, :model_with_brand_name %>

This will provide a dropdown menu containing all the brand names allowing you to pick the correct one for the hardware.