validate_specific_value

This is a way to validate single attribute in Rails. 🎉

Sometimes there are validations that are quite expensive (e.g. validations that need to perform database queries). In that case you need to avoid using valid? because it simply does a lot more than you need. link

Add this line to your application’s Gemfile:

gem 'validate_specific_value'

Add a validation rule to your model.

validates :name, uniqueness: true

And use:

class User < ApplicationRecord
  validates_specific :name
end

Instance context:

user = User.new(name: 'duplicate_name')
user.valid_name?
# => false

user.errors[:name]
# => ["has already been taken"]

Class context:

User.valid_name?('duplicate_name')
# => false

The implementation is quite simple.

class User < ApplicationRecord
  def valid_name?
    errors.clear
    self.class.validators_on(:name).each do |validator|
      validator.validate_each(self, :name, self[:name])
    end
    errors.empty?
  end
end

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features