Validates at Least One

When validating a has_many relationship, you might want to ensure at least one of the related items is valid.

Set :base_message => true and :message => "Blah blah" to display an error message for the entire object Set :attribute_messages => true to display the individual attribute error messages. Set :required_field to an attribute of your object, i.e. :name to display the base message if that field is blank and the attribute messages otherwise.

Example

class Language < ActiveRecord::Base belongs_to :person validates_presence_of :name end

class Person < ActiveRecord::Base has_many :languages

validates_presence_of :name
validates_at_least_one :languages, :message => "enter at least one language"

end

class Person < ActiveRecord::Base has_many :languages

validates_presence_of :name
validates_at_least_one :languages,
    :base_message => false, :attribute_messages => true,
    :message => "enter at least one language"

end

p = Person.new(:name => "Bob") p.valid? # false p.languages << Language.new p.valid? # false p.languages << Language.new p.valid? # false p.language.first.name = 'en' p.valid? # true

Copyright (c) 2010 Paul Schreiber, released under the MIT license