ActiveRecord stores validation errors in an array called errors. If you have a User model then you would access the validation errors in a given instance like so:
@user = User.create[params[:user]] # create will automatically call validators
if @user.errors.any? # If there are errors, do something
# You can iterate through all messages by attribute type and validation message
# This will be something like:
# attribute = 'name'
# message = 'cannot be left blank'
@user.errors.each do |attribute, message|
# do stuff for each error
end
# Or if you prefer, you can get the full message in single string, like so:
# message = 'Name cannot be left blank'
@users.errors.full_messages.each do |message|
# do stuff for each error
end
# To get all errors associated with a single attribute, do the following:
if @user.errors.include?(:name)
name_errors = @user.errors[:name]
if name_errors.kind_of?(Array)
name_errors.each do |error|
# do stuff for each error on the name attribute
end
else
error = name_errors
# do stuff for the one error on the name attribute.
end
end
end
Of course you can also do any of this in the views instead of the controller, should you want to just display the first error to the user or something.