Add Create A Custom Named References Column as a Rails til

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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@@ -649,6 +649,7 @@ _1068 TILs and counting..._
 - [Comparing DateTimes Down To Second Precision](rails/comparing-datetimes-down-to-second-precision.md)
 - [Conditional Class Selectors in Haml](rails/conditional-class-selectors-in-haml.md)
 - [Convert A Symbol To A Constant](rails/convert-a-symbol-to-a-constant.md)
+- [Create A Custom Named References Column](rails/create-a-custom-named-references-column.md)
 - [Creating Records of Has_One Associations](rails/creating-records-of-has-one-associations.md)
 - [Custom Validation Message](rails/custom-validation-message.md)
 - [Customize Paths And Helpers For Devise Routes](rails/customize-paths-and-helpers-for-devise-routes.md)

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

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+# 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,
+
+```ruby
+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.
+
+```ruby
+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.
+
+[source](https://stackoverflow.com/a/42056089/535590)