Specifying column name in a "references" migration

In Rails 4.2+ you can also set foreign keys in the db as well, which is a great idea.

For simple associations this can be done also on t.references adding foreign_key: true, but in this case you'll need two lines.

# The migration
add_reference :posts, :author, index: true
add_foreign_key :posts, :users, column: :author_id

# The model
belongs_to :author, class_name: "User"

For Rails 5+

Initial Definition:

If you are defining your Post model table, you can set references, index and foreign_key in one line:

t.references :author, index: true, foreign_key: { to_table: :users }

---

Update Existing:

If you are adding references to an existing table, you can do this:

add_reference :posts, :author, foreign_key: { to_table: :users }

---

^{Note: The default value for index is true.}