Objective-C Fundamentals

The iPhone SDK: Safari
315
C.2 Alternatives to Objective-C and Cocoa
Out of the box, Xcode and the iPhone software development kit (SDK) support
development of applications in C, C++, and their Objective-C-based variants, but this
doesn’t mean they’re the only options open to developers. A number of third parties
offer alternative development tools to suit the needs and backgrounds of almost
any developer.
Of these alternatives, a lot of attention has been concentrated on those that enable
applications to be developed in scripting languages such as Lua or Ruby or that use
technologies such as HTML, Cascading Style Sheets (CSS), and JavaScript, which are
more familiar to client-side web developers. It’s commonly perceived that these types
of tools can offer a quicker and perhaps more productive work environment, much in
the way that Objective-C and other Smalltalk-inspired languages were considered an
improvement over C and C++.
C.2.1
Close to home: Objective-C++ and plain old C or C++
If you’ve developed for another mobile platform, you likely have some background in
C or C++. A lot of third-party support libraries for a magnitude of purposes, such as
speech synthesis, physics engines, communication, and image analysis, to name a few,
are also developed in these languages.
Xcode can compile C (.c) or C++ (.cpp) source code in an iPhone project just as
easily as it can compile Objective-C (.m) files. Simply add the files to your project and
allow Xcode to build your project as normal. A number of the key frameworks in iOS,
such as Core Graphics, are C-based APIs, so you’re already familiar with integrating
code developed in C or C++ with an Objective-C project.
Unlike Mac OS X, though, iOS doesn’t provide a C-based API for creating GUIs
(there’s no equivalent of Carbon). This means that unless you’re interested in developing
a completely custom UI with OpenGL (another C-based API), your use of C or
C++ source code will probably be restricted to behind-the-scenes logic, which will then
be interfaced to a UI written in Objective-C. This isn’t a bad approach if you want to
share a core set of logic across a number of platforms that support development in C
or C++, such as iOS, Android, Symbian, and Windows Mobile. You can develop your
core logic with C or C++ and then wrap a platform-specific UI layer around it for each
platform you want to support.
Objective-C++ is interesting because it’s, quite literally, the object-oriented features
of Objective-C applied on top of the C++, not C, programming language. This combination
leads to some interesting side effects. As an example, it isn’t possible to derive a
C++ class from an Objective-C class, because no attempt was made to unify their distinct
type systems.
C.3 The iPhone SDK: Safari
When the original iPhone was released, the only way to extend the platform was by
deploying web-based applications. As an Apple press release of the time noted: