How to Change "3 Errors Prohibited This Foobar from Being Saved" Validation Message in Rails

How to change 3 errors prohibited this foobar from being saved validation message in Rails?

The error_messages_for helper that you are using to display the errors accepts a :header_message option that allows you to change that default header text. As in:

error_messages_for 'model', :header_message => "You have some errors that prevented saving this model"

The RubyOnRails API is your friend.

1 error prohibited this {{model}} from being saved

This is a problem with internationalization in rails. One solution that has worked for some is to downgrade the internationalization gem from 0.5.0 to 0.4.2, like so:

sudo gem uninstall i18n
sudo gem install i18n -v 0.4.2

Of course, if you're using RVM to manage your gems, you don't need sudo in the commands above.

How to get number of fields with validation error on rails

obj.errors.keys will give you the columns which have errors, you can do obj.errors.keys.count to get the total number of fields having errors.

Also, it will work for nested attributes because the nested attributes column having error will come as nested_model.nested_model_column_name

Rails 4: remove attribute name from error message in custom validator

Unfortunately currently the format of full_messages for errors is controlled with a single I18n key errors.format, hence any change to it will have a global consequences.

Common option is to attach error to the base rather than to the attribute, as full messages for base errors do not include attribute human name. Personally I don't like this solution for number of reason, main being that if the validation error is caused by a field A, it should be attach to field A. It just makes sense. Period.

There is no good fix for this problem though. Dirty solution is to use monkey patching. Place this code in a new file in your config/initializers folder:

module ActiveModel
  class Errors
    def full_message(attribute, message)
      return message if attribute == :base
      attr_name = attribute.to_s.tr('.', '_').humanize
      attr_name = @base.class.human_attribute_name(attribute, :default => attr_name)
      klass = @base.class
      I18n.t(:"#{klass.i18n_scope}.error_format.#{klass.model_name.i18n_key}.#{attribute}", {
                                 :default   => [:"errors.format", "%{attribute} %{message}"],
                                 :attribute => attr_name,
                                 :message   => message
                             })
    end
  end
end

This preserves the behaviour of full_messages (as per rails 4.0), however it allows you to override the format of full_message for particular model attribute. So you can just add this bit somewhere in your translations:

activerecord:
  error_format:
    post:
      copy: "%{message}"

I honestly dislike the fact that there is no clean way to do this, that probably deserves a new gem.

show validation error message from rails model

You can add errors to your instance using

self.errors.add(:base, "your message here")

You could put attributes name as symbol instead of :base or whatever you like.

In your case

if self.RJan.nil? && self.RFeb.nil? && self.RMar.nil? && self.R1.nil?
  self.errors.add(:base, "your message here")
end

Rails: Why can't I save a new model Instance to the database?

class PagesController
  # POST /pages
  def create
    @page = Page.new(page_params) do |page|
      # smelly - should be handled inside the model not by the controller
      page.slug = helpers.create_slug_from_title(page.title)
    end
    if @page.save
      redirect_to @page, status: :created
    else
      render :new, status: :unprocessable_entity
    end
  end

  private

  def page_params
    params.require(:page)
          .permit(:foo, :bar, :title)
  end
end

You handle invalid user input in a classic web app by re-rendering the form. begin ... rescue will not work here as .save does not raise. save! does but its use here is questionable as exceptions should be used for exceptional cases - invalid user input is an everyday event.

On the form you use the errors object to diplay the validation errors to the user:

<%= form_with(model: @page) do |f| %>
  <% # @todo extract this into a partial %>
  <% if f.object.errors.any? %>
  <div id="error_explanation">
    <h2><%= pluralize(f.object.errors.count, "error") %> prohibited this page from being saved:</h2>
    <ul>
    <% f.object.errors.full_messages.each do |msg| %>
      <li><%= msg %></li>
    <% end %>
    </ul>
  </div>
  <% end %>
  
  <div class="field">
    <%= f.label :title %>
    <%= f.text_field :title %>
  </div>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

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