How would you choose betwe...

Choosing between belongs_to and has_one in Ruby on Rails depends on the direction of the relationship and where the foreign key is stored. Here’s a detailed explanation to help you understand and decide which one to use:

Understanding the Relationship

1. belongs_to Association:

   • The belongs_to association is used when the model declaring it contains the foreign key.
   • It indicates that the current model holds a reference to another model.
   • Example: If an Account belongs to a Supplier, the accounts table will have a supplier_id column.
   • Code Example:
     ruby Copy

     class Account < ApplicationRecord
       belongs_to :supplier
     end

2. has_one Association:

   • The has_one association is used when the other model contains the foreign key.
   • It indicates that the current model is referenced by another model.
   • Example: If a Supplier has one Account, the accounts table will have a supplier_id column.
   • Code Example:
     ruby Copy

     class Supplier < ApplicationRecord
       has_one :account
     end

Key Differences

• Foreign Key Placement:

  • belongs_to: The foreign key is in the table of the model declaring the belongs_to association.
  • has_one: The foreign key is in the table of the other model.

• Semantic Meaning:

  • belongs_to: Indicates ownership or a direct reference to another model.
  • has_one: Indicates that another model references this model.

Practical Example

Consider a scenario with Supplier and Account models:

• A Supplier has one Account.
• An Account belongs to a Supplier.

The corresponding migrations might look like this:

class CreateSuppliers < ActiveRecord::Migration[7.1]
  def change
    create_table :suppliers do |t|
      t.string :name
      t.timestamps
    end

    create_table :accounts do |t|...