ONLamp.com_ Ajax on Rails

In the beginning, there was the World Wide Web. Compared with desktop applications, web applications were slow and clunky. People liked web applications anyway because they were conveniently available from anywhere, on any computer that had a browser. Then Microsoft created XMLHttpRequest in Internet Explorer 5, which let browser-side JavaScript communicate with the web server in the background without requiring the browser to display a new web page. That made it possible to develop more fluid and responsive web applications. Mozilla soon implemented XMLHttpRequest in its browsers, as did Apple (in the Safari browser) and Opera.

XMLHttpRequest must have been one of the Web's best kept secrets. Since its debut in 1998, few sites have used it at all, and most developers, if they even knew about it, never used it. Google started to change that when it released a series of high-profile web applications with sleek new UIs powered by XMLHttpRequest. The most visually impressive of these is Google Maps, which gives you the illusion of being able to drag around an infinitely sizable map in its little map window.

Highlighted by techieme

How Rails Implements Ajax

Rails has a simple, consistent model for how it implements Ajax operations.

Once the browser has rendered and displayed the initial web page, different user actions cause it to display a new web page (like any traditional web app) or trigger an Ajax operation:

1. A trigger action occurs. This could be the user clicking on a button or link, the user making changes to the data on a form or in a field, or just a periodic trigger (based on a timer).
2. Data associated with the trigger (a field or an entire form) is sent asynchronously to an action handler on the server via XMLHttpRequest.
3. The server-side action handler takes some action (that's why it is an action handler) based on the data, and returns an HTML fragment as its response.
4. The client-side JavaScript (created automatically by Rails) receives the HTML fragment and uses it to update a specified part of the current page's HTML, often the content of a <div> tag.

An Ajax request to the server can also return any arbitrary data, but I'll talk only about HTML fragments. The real beauty is how easy Rails makes it to implement all of this in your web application.

Highlighted by buzzart

Highlighted by mgibbons

Highlighted by nekochat

Highlighted by lacher