Check username availability

Question

I have a form to user login:

<%= form_tag(@action, :method => "post", :name => 'signup' ,:onSubmit => 'return validate();') do %>    
  <%= label_tag(:user, "Username:") %>
  <%= text_field_tag(:user) %>

I want to check if there is the username in the database immediately after :user-field lost focus. I can override this event on the form with javascript, but I can not send Ruby-AJAX request from javascipt code.

Is there any way to check username without adding additional controls (buttons, links) on the form?

Answer 1

You can use some JavaScript (this one written with jQuery) for AJAX cheking:

$(function() {
    $('[data-validate]').blur(function() {
        $this = $(this);
        $.get($this.data('validate'), {
            user: $this.val()
        }).success(function() {
            $this.removeClass('field_with_errors');
        }).error(function() {
            $this.addClass('field_with_errors');
        });
    });
});

This JavaScript will look for any fields with attribute data-validate. Then it assings onBlur event handler (focus lost in JavaScript world). On blur handler will send AJAX request to the URL specified in data-validate attribute and pass parameter user with input value.

Next modify your view to add attribute data-validate with validation URL:

<%= text_field_tag(:user, :'data-validate' => '/users/checkname') %>

Next add route:

resources :users do
  collection do
    get 'checkname'
  end
end

And last step create your validation:

class UsersController < ApplicationController
  def checkname
    if User.where('user = ?', params[:user]).count == 0
      render :nothing => true, :status => 200
    else
      render :nothing => true, :status => 409
    end
    return
  end

  #... other controller stuff
end