---
title: "Rails 6 adds private option to delegate method"
description: "Rails 6 adds private option to delegate method"
canonical_url: "https://www.bigbinary.com/blog/rails-6-adds-private-option-to-delegate-method"
markdown_url: "https://www.bigbinary.com/blog/rails-6-adds-private-option-to-delegate-method.md"
---

# Rails 6 adds private option to delegate method

Rails 6 adds private option to delegate method

- Author: Amit Choudhary
- Published: June 10, 2019
- Categories: Rails 6, Rails

Rails 6 adds `:private` option to
[delegate](https://api.rubyonrails.org/v5.2/classes/Module.html#method-i-delegate)
method. After this addition, we can delegate methods in the private scope.

Let's checkout how it works.

#### Rails 6.0.0.beta2

Let's create two models named as `Address` and `Order`. Let's also delegate
`validate_state` method in `Order` to `Address`.

```ruby
class Address < ApplicationRecord
  validates :first_name, :last_name, :state, presence: true

  DELIVERABLE_STATES = ['New York']

  def validate_state
    unless DELIVERABLE_STATES.include?(state)
      errors.add(:state, :invalid)
    end
  end
end

class Order < ApplicationRecord
  belongs_to :address

  delegate :validate_state, to: :address
end

>> Order.first
SELECT "orders".* FROM "orders"
ORDER BY "orders"."id" ASC LIMIT $1  [["LIMIT", 1]]

=> #<Order id: 1, amount: 0.1e2, address_id: 1, created_at: "2019-03-21 10:02:58", updated_at: "2019-03-21 10:17:44">

>> Address.first
SELECT "addresses".* FROM "addresses"
ORDER BY "addresses"."id" ASC LIMIT $1  [["LIMIT", 1]]

=> #<Address id: 1, first_name: "Amit", last_name: "Choudhary", state: "California", created_at: "2019-03-21 10:02:47", updated_at: "2019-03-21 10:02:47">

>> Order.first.validate_state
SELECT "orders".* FROM "orders"
ORDER BY "orders"."id" ASC LIMIT $1  [["LIMIT", 1]]

SELECT "addresses".* FROM "addresses"
WHERE "addresses"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]

=> ["is invalid"]
```

Now, let's add `private: true` to the delegation.

```ruby
class Order < ApplicationRecord
  belongs_to :address

  delegate :validate_state, to: :address, private: true
end

>> Order.first.validate_state
SELECT "orders".* FROM "orders"
ORDER BY "orders"."id" ASC LIMIT $1  [["LIMIT", 1]]

=> Traceback (most recent call last):
        1: from (irb):7
NoMethodError (private method 'validate_state' called for #<Order:0x00007fb9d72fc1f8>
Did you mean?  validate)
```

As we can see, Rails now raises an exception of private method called if
`private` option is set with `delegate` method.

Here is the relevant [pull request](https://github.com/rails/rails/pull/31944).

## Links

- [Human page](https://www.bigbinary.com/blog/rails-6-adds-private-option-to-delegate-method)