Rails 3 with composed_of model and validation

问题

I have this domain model:

class Person < ActiveRecord::Base
  composed_of :address,
              mapping: [%w(address_street street), %w(address_city city), %w(address_zip_code zip_code), %w(address_country country)]

  validates :name, presence: true, length: { maximum: 50 }
  validates :surname, presence: true, length: { maximum: 50 }

  validates_associated  :address
end

class Address
  include ActiveModel::Validations
  include ActiveModel::Conversion
  extend ActiveModel::Naming

  attr_reader :street, :city, :zip_code, :country

  validates :street, presence: true
  validates :city, presence: true
  validates :zip_code, presence: true
  validates :country, presence: true

  def initialize(street, city, zip_code, country)
    @street, @city, @zip_code, @country = street, city, zip_code, country
  end

  def ==(other_address)
    street == other_address.street && city == other_address.city && zip_code == other_address.zip_code && country == other_address.country
  end

  def persisted?
    false
  end
end

When I try to save an invalid model:

> p = Person.new
=> #<Person id: nil, name: nil, surname: nil, address_street: nil, address_city: nil, address_zip_code: nil, address_country: nil
> p.valid?
=> false
> p.errors
=> {:name=>["can't be blank"], :surname=>["can't be blank"], :address=>["is invalid"]}

This is ok, but I would prefer to have the error array filled with the error messages of Address, like this:

=> {:name=>["can't be blank"], :surname=>["can't be blank"], :address_street=>["can't be blank"], :address_city=>["can't be blank"], :address_zip_code=>["can't be blank"], :address_country=>["can't be blank"]}

The question is: is there a clean Rails way to do it? Or simply I have to move the validation code from Address to Person (pretty ugly)? Any other solution?

Thank you very much.

回答1:

When you define a composed_of attribute, it becomes an object on it's own. I see two ways to answer your need.

1) add error message in your Address class

Replace your current validations with:

validates_each :street, :city, :zip_code, :country do |record, attr, value|  
  record.errors.add attr, 'should not be blank' if value.blank?
end

This way, you'll be able to access the error messages doing:

p = Person.new
p.address.errors

2) Customize only the address error message

validates_associated  :address, 
                      :message => lambda { |i18n_key, object| self.set_address_error_msg(object[:value]) }

def self.set_address_error_msg address
  errors_array = Array.new
  address.instance_variables.each do |var|
    errors_array << "#{var[1..-1]} should not be blank" if address.send(var[1..-1]).blank?
  end
  errors_array.join(", ")
end       

This would render something like:

=> #<OrderedHash {:address=>["country should not be blank, zip_code should not be blank, validation_context should not be blank, city should not be blank"]}> 

Finally, you could rewrite validators in your Profile class but as you said it's really ugly.

来源：https://stackoverflow.com/questions/6707636/rails-3-with-composed-of-model-and-validation