method

add_reference

v4.0.2 - Show latest stable - Class: ActiveRecord::ConnectionAdapters::SchemaStatements

add_reference(table_name, ref_name, options = {})

public

Adds a reference. Optionally adds a type column, if :polymorphic option is provided. add_reference and add_belongs_to are acceptable.

Create a user_id column

add_reference(:products, :user)

Create a supplier_id and supplier_type columns

add_belongs_to(:products, :supplier, polymorphic: true)

Create a supplier_id, supplier_type columns and appropriate index

add_reference(:products, :supplier, polymorphic: true, index: true)

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 604
      def add_reference(table_name, ref_name, options = {})
        polymorphic = options.delete(:polymorphic)
        index_options = options.delete(:index)
        add_column(table_name, "#{ref_name}_id", :integer, options)
        add_column(table_name, "#{ref_name}_type", :string, polymorphic.is_a?(Hash) ? polymorphic : options) if polymorphic
        add_index(table_name, polymorphic ? ]id type].map{ |t| "#{ref_name}_#{t}" } : "#{ref_name}_id", index_options.is_a?(Hash) ? index_options : nil) if index_options
      end

1Note

foreign_key option

cmbankester · Jun 7, 2016

It is also possible to specify that +add_foreign_key+ should be added to the schema: add_reference(:products, :supplier, foreign_key: true)