December 2010
Beginner to intermediate
320 pages
10h 3m
English
Content preview from Learning the iOS 4 SDK for JavaScript ProgrammersBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Downloading Remote Files Asynchronously
The JavaScript language seemed to transform from “toy language” to
“serious language” when all mainstream browsers implemented the XMLHttpRequest object or similar functionality (it began life as an
ActiveX control for Internet Explorer). Suddenly browsers could silently
(and under more control than before) communicate with a server and update
portions of a web page’s content without having to reload or redraw the
entire page. Web pages could look more like apps. And thus web apps were
truly born. In 2005, Jesse James Garrett described the activity with this
object as Asynchronous JavaScript and XML, or Ajax.
Background communication for standalone applications is nothing new,
and iOS provides a class that performs the work for which you’ve been
using Ajax on the Web. Some of the concepts are the same, but the iOS
version is heavily reliant on the delegate pattern, which makes it easy to
grasp (IMHO). Although the XMLHttpRequest object automatically accumulates
data into a buffer, you have to manage that accumulation in your iOS code.
But it’s a pretty easy task to take care of and shouldn’t cause you any
headaches.
You will gain one enormous freedom over Ajax on the Web: there are no same-origin security restrictions on you. If you have a publicly accessible URL, your app can download the data and manipulate it to your heart’s content.
It’s likely a waste of time to compare fine points between the two systems, because so many web authors use ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.