Full on Errors

ActiveRecord’s full\_messages method is a useful one for many reasons. I like using it as a message for tests that fail for strange reasons. I like it for displaying error messages in a view, which is simpler than modifying how error\_messages\_for displays. However, I have always found it annoying that I cannot ask an ActiveRecord object for the full-messages on a specific attribute … until now.

To remedy this, I wrote the full\_on\_errors plugin which simply adds a full\_on method to the Errors class of an ActiveRecord instance. It’s use is simple; simply call full_on and pass the attribute for which you would like the full messages for.

Example

In fact, it’s so simple that examples are coming in the third paragraph. Let’s say you have a User model that looks like the following:

class User < ActiveRecord::Base
  validates_presence_of :name
  validates_presence_of :email
end

Ignoring the fact that you could one-line the validation, if you were to validate a new instance of User that does not provide name or email, you would receive two error messages. With full\_messages, what would return would look like the following:

user = User.new
user.valid?
=> false
user.errors.full_messages
=> ["Name can't be blank", "Email can't be blank"]

But, what if you wanted the full-messages for just the name attribute? You could look for those errors that start with name; you could live with user.errors.on(:name) returning an array of partial error message; or you could do the following:

user = User.new
user.valid?
=> false
user.errors.full_on(:name)
=> ["Name can't be blank"]

Installation

Step 1: install the Rails plugin:

$RAILS_ROOT> ./script/plugin install \
  http://glomp.rubyforge.org/svn/plugins/full_on_errors

Step 2: Start using it

Code

The code is extremely simple and is - oddly enough - based on Errors.full\_messages. I have simplified the full\_messages code to focus on one attribute, to do less, and to look better (according to Gus Aesthetics):

module Glomp #:nodoc:
  module FullOnErrors #:nodoc:
    def full_on(attr_name)
      attr = attr_name.to_s
      errs = on(attr).to_a
      return errs if attr == 'base'
      human_name = @base.class.human_attribute_name(attr)
      errs.map {|msg| "#{human_name} #{msg}"}
    end
  end # FullOnErrors
end # Glomp

ActiveRecord::Errors.send(:include, Glomp::FullOnErrors)

For comparison’s sake, here is the full\_messages code from the Errors class:

# Returns all the full error messages in an array.
def full_messages
  full_messages = []

  @errors.each_key do |attr|
    @errors[attr].each do |msg|
      next if msg.nil?

      if attr == "base"
        full_messages << msg
      else
        full_messages << @base.class.human_attribute_name(attr) + " " + msg
      end
    end
  end
  full_messages
end