ExpressValidations

This gem allows you to express the validations in your Rails models as JSON objects, so that you can implement them as client side validations with Javascript – the way you want to.

It helps to maintain consistency between validation rules on server-side and implementations on client-side.

It can be very handy if you want to display validations in a more user-friendly manner or when you are creating a wizard and want to implement model validations on each step.

Add this line to your Rails application's Gemfile:

gem 'express_validations'

And then execute:

$ bundle

Or install it yourself as:

$ gem install express_validations

For model classes where you require the validations on client-side, add the following line to it:

include ExpressValidations

Then in the views for this model do:

<%= javascript_tag do %>
	window.validationRules = <%= #{Your Model}.validations_as_json.html_safe %>;
<% end %>

This will give access of the model's validation definitions to your application's client-side.

You can also use the Javascript functions provided with this gem to check:

• if validation passes on a particular field or form
• get validation details for a field or a set of fields.

Include the following line in your application.js file:

//= require express.validations

Then you can use the included functions, for examples, as:

// returns true or false
var fieldValidation = expressValidations.checkFieldValidation($('input#user_first_name'), window.validationRules);

// returns true or false
var formValidation = expressValidations.checkFieldValidation($('form#new_user'), window.validationRules);

// returns an object
var fieldValidationRules = expressValidations.getValidationsFor($('input#user_first_name'), window.validationRules);

// returns an array of objects
var multipleFieldsValidationRules = expressValidations.getValidationsForMultiple([$('input#username'), $('input#password')], window.validationRules);

Uniqueness validation should be checked only when all other validations on the field(s) have passed. So it is done through a separate Javascript function.

If you have a GET route called determine_uniqueness defined on the relative controller, you can use the provided Javascript function, something like the example below.

var checkUniquenessResult, uniquenessResults;

// if other validations on the field(s) have passed
if (validationPassed) {
  uniquenessResults = []; // using an array is essential, since it is updated via reference
  window.networkError = false; // in case of network error this is set to true

  // in case there are multiple fields to check
  $.each(validateFields, function(i1, $validationField) {
    // returns a 2D array of elements and their uniqueness results
    uniquenessResults = expressValidations.checkUniqueness($validationField, uniquenessResults);
  });

  // use setInterval in case you want to wait for the result before continuing with the form submission process
  checkUniquenessResult = setInterval(function() {
    if (uniquenessResults.count == validateFields.count) {
      clearInterval(checkUniquenessResult);
      if (window.networkError) {
        alert("Network error. Please try again later.");
      } else if (this2DArrayContains(false, uniquenessResults)) { // define a function to check any false in the uniquenessResults 2D array, against any element
        // define a function to display validation result
        displayUniquenessValidation(uniquenessResults, window.validationRules);
      } else {
        // code to continue with form submission to process
      }
    }
  }, 200);
}

You can define your controller method like this:

def determine_uniqueness
  field_name, with_value = params[:field], params[:value]
  ## define a class method to check uniqueness
  uniqueness = User.check_uniqueness_for(field_name, with_value)

  respond_to do |format|
    format.json { render json: { uniqueness: uniqueness } }
  end
end

• It requires Ruby >= 1.9.3
• It requires activesupport >= 3.2.22
• It requires that you declare validations with the form validates_#{validation_name}_of such as validates_presence_of, with specified options and messages
• It skips on numericality validator
• It cannot take custom validations into account

• Add more JS examples
• Add the numericality validator
• Add tests for Javascript functions

Bug reports and pull requests are welcome on GitHub at https://github.com/vikramanity/express_validations.

The gem is available as open source under the terms of the MIT License.