Objective-C Fundamentals
Objective-C Fundamentals
Objective-C Fundamentals
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The iPhone SDK: Safari<br />
319<br />
It’s important to note that web applications currently—and probably always will—<br />
have<br />
less access to hardware features and operating system services than do <strong>Objective</strong>-C<br />
applications. Examples of features currently accessible only from <strong>Objective</strong>-C include<br />
the user’s address book, camera photo library, and iPod music. Constant improvements<br />
are being made in this regard; for example, iPhone OS 3.0 introduced the capability<br />
for web applications to access GPS location information, and iOS 4.2 added<br />
access to accelerometer data. But the web application platform will always present the<br />
developer with a subset of the features accessible to native developers, if only because<br />
Apple engineers must expend additional effort to produce JavaScript-accessible wrappers<br />
for any feature they want to expose to web applications, and additional security<br />
and privacy concerns arise with features that can be accessed by any website.<br />
C.3.3<br />
PhoneGap and other extensible cross-platform solutions<br />
Developers need not abandon HTML, CSS, and JavaScript as their development platforms<br />
if they find the built-in services of the Safari web browser and web-based applications<br />
inadequate for their application needs.<br />
A number of solutions exist to enable applications written in web-based technologies<br />
to run outside of the traditional Safari browser–based environment and, in the<br />
process, to gain greater access to system hardware. One example of this approach is a<br />
development tool called PhoneGap (www.phonegap.com). PhoneGap is an open<br />
source product that enables you to build applications in HTML and JavaScript. Unlike<br />
a web application running in Safari, however, your JavaScript source code also has<br />
access to the PhoneGap SDK APIs, which provide access to additional features of the<br />
mobile platform, such as Geolocation, Vibration, Accelerometer, Contacts, and Sound.<br />
This accessibility is achievable because a PhoneGap application is a native iOS<br />
application, built using <strong>Objective</strong>-C and Xcode, just as we’ve discussed throughout<br />
this book. Most of the application is a predeveloped <strong>Objective</strong>-C component (which<br />
for the most part is hidden and automatically inserted by the project template) that<br />
sets up a UIWebView control to display the HTML and JavaScript content embedded in<br />
you Xcode project. The magic occurs because the <strong>Objective</strong>-C component exposes<br />
additional services that your JavaScript can hook into. All your web application must<br />
do is include a element that imports the main PhoneGap JavaScript file.<br />
Appearing as a standard <strong>Objective</strong>-C-based iOS application, at least from the outside,<br />
means PhoneGap applications can be distributed via the iTunes App Store,<br />
which provides an easy monetization and consumer discovery/marketing approach.<br />
Because the core of your PhoneGap application is written in HTML, CSS, and<br />
JavaScript, it’s fairly portable across most mobile platforms, so it shouldn’t surprise<br />
you that the native part of PhoneGap is available for a number of platforms, including<br />
Android, Windows Mobile, iPhone, and Blackberry. By combining your platformagnostic<br />
JavaScript with a device-specific shell that deals with setting up a web<br />
browser control, then wrapping the device’s features into a consistent PhoneGap<br />
JavaScript-based API, you can have your cake and eat it too—developing iPhone
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