Question

How I can do or generate a migration with a foreign key? I have municipios table, and I want to relate with the table ciudades, the table will have these fields: nombre_id (name id), nombre (name), departamento (department) in this case how I can run the scaffold script to generate the foreign key migration?

Answer 1

If you mean that you want to create the migration file the command is

rails generate migration NAME [field:type field:type] [options]

or shortcut

rails g migration NAME [field:type field:type] [options]

But if you want to create a scaffold from model that referencing other model. Maybe you could do it like this

create ciudades model with scaffold

rails g scaffold ciudades nombre_id:integer nombre:integer departamento:string

create municipios model that reference ciudades

rails g scaffold municipios ciudades:references

this will create attribute ciudades_id on the municipios table.
The migration should look like this.

class CreateMunicipios < ActiveRecord::Migration
  def self.up
    create_table :municipios do |t|
      t.references :ciudades

      t.timestamps
    end
  end

  def self.down
    drop_table :municipios
  end
end

also on the municipios model it will create the belongs_to relation.

but this does not update the cuidades model. You have to specify the relation.

Also keep in mind that rails automatically create id field on a model. it is the convention. if you mean that nombre_id is the primary key, you have to specify it your self.

Hope this help