undefined method `error_message_on' after implementing simple private messages [duplicate] - ruby-on-rails

Question

I have a form with input fields/labels etc. How do I get the error message to show up next to the field? instead of clumped together at the top?
I am using devise, rails 3
I have this at the top of my form:
= form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f|
- if resource.errors.any?
#errorExplanation
%h2
= pluralize(resource.errors.count, "error")
prevented this user from being saved:
%ul
- resource.errors.full_messages.each do |msg|
%li
= msg

Answer 1

You can use this
- if #resource.errors[:field_name]
...
Also useful link:
http://guides.rubyonrails.org/active_record_validations.html#working-with-validation-errors

Answer 2

Just create a file in your initializers folder.
config/initializers/inline_errors.rb
Place this code in it:
ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
unless html_tag =~ /^<label/
%{<div class="has-error">#{html_tag}<span class="help-block">#{instance.error_message.first}</span></div>}.html_safe
else
%{#{html_tag}}.html_safe
end
end
PD: Sorry for my english.

Answer 3

How about this
if you want to put the error message just beneath the text field, you can do like this
.row.spacer20top
.col-sm-6.form-group
= f.label :first_name, "*Your First Name:"
= f.text_field :first_name, :required => true, class: "form-control"
= f.error_message_for(:first_name)
What is error_message_for?
--> Well, this is a beautiful hack to do some cool stuff
# Author Shiva Bhusal
# Aug 2016
# in config/initializers/modify_rails_form_builder.rb
# This will add a new method in the `f` object available in Rails forms
class ActionView::Helpers::FormBuilder
def error_message_for(field_name)
if self.object.errors[field_name].present?
model_name = self.object.class.name.downcase
id_of_element = "error_#{model_name}_#{field_name}"
target_elem_id = "#{model_name}_#{field_name}"
class_name = 'signup-error alert alert-danger'
error_declaration_class = 'has-signup-error'
"<div id=\"#{id_of_element}\" for=\"#{target_elem_id}\" class=\"#{class_name}\">"\
"#{self.object.errors[field_name].join(', ')}"\
"</div>"\
"<!-- Later JavaScript to add class to the parent element -->"\
"<script>"\
"document.onreadystatechange = function(){"\
"$('##{id_of_element}').parent()"\
".addClass('#{error_declaration_class}');"\
"}"\
"</script>".html_safe
end
rescue
nil
end
end
Result
Markup Generated after error
<div id="error_user_first_name" for="user_first_name" class="signup-error alert alert-danger">This field is required.</div>
<script>document.onreadystatechange = function(){$('#error_user_first_name').parent().addClass('has-signup-error');}</script>
Corresponding SCSS
.has-signup-error{
.signup-error{
background: transparent;
color: $brand-danger;
border: none;
}
input, select{
background-color: $bg-danger;
border-color: $brand-danger;
color: $gray-base;
font-weight: 500;
}
&.checkbox{
label{
&:before{
background-color: $bg-danger;
border-color: $brand-danger;
}
}
}
Note: Bootstrap variables used here
and, do not forget to Restart the server now and after any modification to the file in config dir.

Answer 4

You can use error_message_on
http://apidock.com/rails/ActionView/Helpers/ActiveRecordHelper/error_message_on
Update:
form.error_messages was removed from Rails and is now available as a plugin. Please install it with rails plugin install git://github.com/rails/dynamic_form.git.

Answer 5

If anyone is looking for a way how to display error messages for particular field in Rails 6:
a = Post.new
a.save # => false
a.errors.full_messages_for(:title)
["Title can't be blank"]
a.errors.full_messages_for(:title).join(', ')
"Title can't be blank, Title too short"