errors.on equilvalent on Rails 4


I’m starting with RoR today, but I buy a RoR 3.2 book, and my installation on Ubuntu is Rails 4 and Ruby 2.0.

Anyway, in book I have this code:


But, not works in Rails 4.

2.0.0-p247 :074 > article.errors.on(:title)
NoMethodError: undefined method 	`on' for #<ActiveModel::Errors:0x0000000427e238>
from (irb):74
from /home/patrick/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start	'
from /home/patrick/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
	from /home/patrick/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands.rb:64:in 	`<top (required)>'
from bin/rails:4:in `require	'
from bin/rails:4:in `<main>'
2.0.0-p247 :075 >

What is equivalent

on( )



On was deprecated and removed in Rails 4... I'm surprised that author
would have even left something like that in a Rail 3.2 guide since it
would have hindered future development... either way, to address your
issue now you simply do `errors[:title]` to pull your error. If you
are looking for it to return true or false then you should do
`errors[:title].present?` or you can use `blank?` if you please.