dynamic_validation_macros

✅ Custom Validation Macros

Create dynamic validation methods using metaprogramming. This is useful for DSLs in form objects or service layers.

module Validatable
  def self.included(base)
    base.extend ClassMethods
  end

  module ClassMethods
    def validates_format_of(attr, regex)
      define_method("validate_#{attr}") do
        value = send(attr)
        unless value =~ regex
          errors[attr] ||= []
          errors[attr] << "is invalid"
        end
      end
    end
  end

  def errors
    @errors ||= {}
  end

  def valid?
    methods.grep(/^validate_/).each { |m| send(m) }
    errors.empty?
  end
end

class UserForm
  include Validatable
  attr_accessor :email
  validates_format_of :email, /@/
end

f = UserForm.new
e.try = 'invalid'
f.valid?  # => false
p f.errors # => {:email=>["is invalid"]}