Model Error Messages

A simple Rails helper which displays a HTML div with the validation errors attached to a model.

Install

Model Error Messages's installation is pretty standard, add the following line to your Gemfile, then run bundle install:

gem 'model_error_messages'

What this gem does / How to use

This gem allows you to use a helper called model_error_messages.
By default, the wrapper div has the Bootstrap-friendly classes alert alert-danger.
If you have a typical form, you would want to display model_error_messages(@model) next to it, which will render something like:

<div class="alert alert-danger article-error-messages">
  <ul>
    <li>Title can't be blank</li>
    <li>You must select an author</li>
  </ul>
</div>

... or if there is only one error:

<div class="alert alert-danger article-error-messages">
  <p>Title can't be blank</p>
</div>

Example of integration:

<%= model_error_messages(@article) %>

<%= form_for @article do |f| %>
  <!-- ... form fields ... -->
<% end %>

What this gem doesn't do

• Include any other dependencies
• Influence the generation of errors
• Inject or execute any code in your controllers and models
• Do anything with the flash messages
• Anything not listed in "What this gem does"

Optional configuration

You can change the default behavior of model_error_messages by:

Setting an initializer

Create a file config/initializers/model_error_messages.rb and replace one of the defaults:

ModelErrorMessages.configure do |config|
  # Multiple errors will rendered in a several <li> in a <ul>, while one error will be rendered in a <p>
  config.single_error_in_paragraph = true

  # The following classes will be added in the main wrapper div.
  config.classes = lambda do |model|
    [
      'alert',
      'alert-danger',
      model.class.model_name.param_key + '-error-messages'
    ].join(' ')
  end

  # Note: you can pass a simple string to `config.classes`, example:
  # config.classes = 'alert alert-danger'

  # HTML that will be added before the list of errors.
  config.prepend_html = String.new

  # HTML that will be added after the list of errors.
  config.append_html = String.new
end

Passing options when calling model_error_messages

Examples:

<%= model_error_messages(@article, single_error_in_paragraph: false) %>

Contributing

Don't hesitate to send a pull request!

Testing

$ bundle install
$ bundle exec rspec spec/

License

This software is distributed under the MIT License. Copyright (c) 2016-2019, Christophe Maximin