ruby - Rails associating multiple :has_many -

i'm new rails , trying understand associating entities.

i have 3 entities right now: users, companies, , productlines.

company.rb:

class company < activerecord::base     has_many :users     has_many :productlines end 

user.rb:

class user < activerecord::base   # include default devise modules. others available are:   # :confirmable, :lockable, :timeoutable , :omniauthable   devise :database_authenticatable, :registerable,          :recoverable, :rememberable, :trackable, :validatable    belongs_to :company end 

productline.rb:

class productline < activerecord::base     belongs_to :company end 

i've done migration scrips associate them, when click company on rails admin, i'm getting this:

sqlite3::sqlexception: no such column: productlines.company_id: select "productlines".* "productlines" "productlines"."company_id" = ? extracted source (around line #91):
# def prepare sql stmt = sqlite3::statement.new( self, sql ) return stmt unless block_given?

begin

edit: here migration:

class addproductlineidtocompanies < activerecord::migration   def change     add_column :companies, :productline_id, :integer     add_index :companies, :productline_id   end end 

you should add company_id productlines , not product_line_id companies...

class addcompanyidtoproductlines < activerecord::migration   def change     add_column :productlines, :company_id, :integer   end end