How to display validation error messages with Simple_form but without model?

Question

I use Simple_form in my Rails 4 application.

How can I display error messages in a view that is not tied to a model ?

I want to have the same result than in other views based on models.

For now, this is the code in the view :

<%= simple_form_for(:registration, html: { role: 'form' }, :url => registrations_path) do |f| %>

  <%= f.error_notification %>

  <%= f.input :name, :required => true, :autofocus => true %>
  <%= f.input :email, :required => true %>
  <%= f.input :password, :required => true %>
  <%= f.input :password_confirmation, :required => true %>

  <%= f.button :submit %>

<% end %>

In a 'normal' view (i.e. with a model) the line <%= f.error_notification %> display errors.

What should I do in my controller to initialize something used by Simple_form to display errors ?

Thanks

Answer 1

The simple_form_for helper must wrap a model. But just because we say this doesn't mean it has to be an ActiveRecord model that's backed by a database table. You're free to create models that aren't backed by a database. In Rails 3+ the way to do this is to have your class include the components that you need from ActiveModel. This SO post explains how to do this with an example (and I'm sure there's many others out there). Once you have a model that includes ActiveModel::Validation you can add to the errors collection and then the f.error_notification statement will output the errors as you're used to in table-backed models.

TL;DR: Create a non-ActiveRecord, non-table-backed model then treat it like a regular old model and the form should do the right thing.

Answer 2

Use client_side_validations gem , it is simple , and you've to do only -

<%= simple_form_for(:registration, html: { role: 'form' }, :url => registrations_path) , :validate => true do |f| %> 

But you need to add validations in model also.

Answer 3

Simple Form does not support this functionality "out of the box". But you can add it with a "monkey patch" in an initializer like this (disclaimer - this appears to work for my simple test case but has not been thoroughly tested):

// Put this code in an initializer, perhaps at the top of initializers/simple_form.rb
module SimpleForm
  module Components
    module Errors
      def has_errors?
        has_custom_error? || (object && object.respond_to?(:errors) && errors.present?)
      end

      def errors
        @errors ||= has_custom_error? ? [options[:error]] : (errors_on_attribute + errors_on_association).compact
      end
    end
  end
end

module SimpleForm
  class ErrorNotification
    def has_errors?
      @options[:errors] || (object && object.respond_to?(:errors) && errors.present?)
    end
  end
end

And then you can add errors to your form like this (note you indicate whether to show the error notification by setting 'errors: true', you would have to perform your own check to decide if there are errors present, and add the errors dynamically):

=simple_form_for :your_symbol do |f|
  =f.error_notification errors: true
  =f.input :item1, as: :string, error: "This is an error on item1"
  =f.input :item2, as: :string, error: "This is an error on item2"