til/rails/create-a-custom-named-references-column.md

Create A Custom Named References Column

The t.references and add_reference methods both create a foreign key column name based on the target table.

For instance,

add_reference :guests, :user, foreign_key: true, index: true, null: false

would create a user_id column on the guests table.

At times, you'll need to customize the name of the foreign key column. The Rails migration DSL supports this with the foreign_key option.

Here is an example that shows the syntax for both a new table and an existing table.

class AddInvitedByColumnToUser < ActiveRecord::Migration[6.1]
  def change
    create_table :guests, id: :uuid do |t|
      t.string :email, null: false
      t.timestamps

      t.references :invited_by,
        type: :uuid,
        index: true,
        null: false,
        foreign_key: { to_table: :users }
    end

    add_reference :guests, :signed_up_as,
      type: :uuid,
      index: true,
      null: false,
      foreign_key: { to_table: :users }
  end
end

The t.references call creates a foreign key column to the users table named invited_by. The add_reference call adds a signed_up_as foreign key column to guests that points to users.

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