How can I implement custom validations in Rails?

How can I implement custom validations in Rails?

You can create custom validations in Rails by defining a method in your model and using the validate method.

Can you give me an example of a custom validation?

Sure! For instance, if you want to validate that a user's age is at least 18, you could do something like this:

class User < ApplicationRecord
  validate :age_must_be_at_least_18

  def age_must_be_at_least_18
    if age < 18
      errors.add(:age, 'must be at least 18')
    end
  end
end

What if I want to validate multiple fields?

You can create a custom validation method that checks multiple fields. Just call errors.add for each field that fails validation.

Is there a way to use built-in validators with custom logic?

Yes, you can combine built-in validators with custom logic by using validates along with your custom method.