The Hacker's Notes

Vert.x is an event driven and non blocking “Platform” where we can develop our application on. Vert.x is like Node.JS, but the biggest difference is that it runs on the JVM, it’s scalable, concurrent, non-blocking, distributed and polyglot. Following four key properties of Vert.x helps us in developing reactive applications. Async and non-blocking model Elastic Resilient Responsive Async and non-blocking model None of the Vert.x APIs block the calling thread(with few exceptions). If the result can be found quickly, It will be returned; Otherwise it will be handled by a handler to receive event sometime later. vertx      .createHttpServer()      .requestHandler(r -> {            r.response()            .end("<h1>Hello from my first " + "Vert.x 3 application</h1>"); })      ...

What is validation ? Validations are required for ensuring that the received data is correct and valid. If the received data is valid then we do the further processing with the data. Nested Model Validation Nested model is sometimes tricky when you have complex associations. Here I'm explaining how we can do nested model validation. We use nested form to save associations through its parent model. Generally we do: class Album < ActiveRecord::Base   has_many :songs   accepts_nested_attributes_for :songs end When we are using nested form we want to save a new or edit an existing album with songs. Now suppose we want all the songs to be removed on removal of the album. class Album < ActiveRecord::Base   has_many :songs   accepts_nested_attributes_for :songs, :allow_destroy => true end At this point we can detect and reject empty association entries class Album < ActiveRecord::Base ...

What is "Nested form In Rails 3" and when do we use it? This is a Rails gem for conveniently manage multiple nested models in a single form. It does so in an unobtrusive way through jQuery or Prototype. Example :- Suppose we have two models " Profile " and " Picture ". We want to get all the information in the same form. In this case we got to use "Nested Form". What are the steps to setup nested form gem in your app? Add it to your Gemfile (by writing  gem "nested_form"  to you Gemfile) then run bundle to install it . Asset Pipeline Setup And then add it to the Asset Pipeline in the application.js file: //= require jquery_nested_form and don't forget to do $ bundle install Non Asset Pipeline Setup If you do not use the asset pipeline, run this generator to create the JavaScript file. rails g nested_form:install You can then include the generated JavaScript in your layout. <%= javascript_include_tag :d...