As mentioned, all the tools in the iPhone SDK are installed in the /Developer/Applications folder (when using the default settings). One of those tools is Xcode.

To launch Xcode, double-click the Xcode icon (refer to Figure 1-3). Alternatively, go the quicker route and use Spotlight: Simply type Xcode into the search box and Xcode should be in the Top Hit position.

After Xcode is launched, you see the Welcome screen, shown in Figure 1-4.

Figure 1.4. Figure 1-4

Using Xcode, you can develop different types of iPhone and Mac OS X applications (see Figure 1-5).

Figure 1.5. Figure 1-5

The IDE in Xcode provides many tools and features that make your development life much easier. One such feature is Code Completion (see Figure 1-6), which displays a pop-up list showing the available classes and members (such as methods, properties, and so on).

Figure 1.6. Figure 1-6

The iPhone Simulator (see Figure 1-7) is a very useful tool included in the iPhone SDK that you can use to test your application without using your actual iPhone/iPod Touch. The iPhone Simulator is located in the /Developer/iPhone OS <version>/Platforms/iPhoneSimulator.platform/Developer/Applications/ folder. Most of the time, you don't need to launch the iPhone Simulator directly — running (or debugging) your application in Xcode automatically brings up the iPhone Simulator. Xcode installs the application on the iPhone Simulator automatically.

Figure 1.7. Figure 1-7

The iPhone Simulator can simulate different versions of the iPhone OS (see Figure 1-8). This capability is very useful if you need to support older versions of the platform as well as testing and debugging errors reported in the application on specific versions of the OS.

Figure 1.8. Figure 1-8

Uninstalling Applications from the iPhone Simulator

The user domain of the iPhone OS file system for the iPhone Simulator is stored in the ~/Library/Application Support/iPhone Simulator/User/ folder.

Note

The ~/Library/Application Support/iPhone Simulator/User/ folder is also known as the <iPhoneUserDomain>.

All third-party applications are stored in the <iPhoneUserDomain>/Applications/ folder. When an application is deployed onto the iPhone Simulator, an icon is created on the Home screen (shown on the left in Figure 1-9) and a file and a folder are created within the Applications folder (shown on the right in Figure 1-9).

Figure 1.9. Figure 1-9

To uninstall (delete) an application, execute the following steps:

1. Click and hold the icon of the application in the Home screen until all the icons start wriggling. Observe that all the icons now have an "x" button displayed on their top left corners.

2. Click the x button (see Figure 1-10) next to the icon of the application you want to uninstall.

   

   Figure 1.10. Figure 1-10

3. An alert window appears asking if you are sure you want to delete the icon. Click Delete to confirm the deletion.

Warning

When the application is uninstalled, the corresponding file and folder in the Applications folder are deleted automatically.

To reset the iPhone Simulator to its original state, the easiest way is to select the iPhone Simulator

Interface Builder is a visual tool that allows you to design your user interfaces for your iPhone applications. Using Interface Builder, you drag and drop views on windows and then connect the various views with outlets and actions so that they can programmatically interact with your code.

Figure 1-11 shows the various windows in Interface Builder.

Figure 1.11. Figure 1-11

Appendix C discusses Interface Builder in more detail.

The Instruments (see Figure 1-12) application allows you to dynamically trace and profile the performance of your Mac OS X and iPhone applications.

Figure 1.12. Figure 1-12

Using Instruments, you can:

At the time of writing, the iPhone OS is in its third revision — that is, version 3.0. The iPhone OS has gone through several revisions, and the major versions are as follows:

For a detailed description of the features in each release, check out http://en.wikipedia.org/wiki/IPhone_OS_version_history.

One of the most common complaints that beginning iPhone programmers made was about the inability to test iPhone applications they have developed on their actual devices. It seems odd that as the owner of the device, they can't even test their applications on it. Turns out that for security reasons, Apple requires all applications to be signed with a valid certificate, and for testing purposes, a developer certificate is required.

To test your applications on a device, you must sign up for the iPhone Developer program and request that a developer certificate be installed onto your device. This is a lengthy process, but I give you detailed help with it in Appendix E.

The iPhone is a beautiful device with a high-resolution screen. At 3.5 inches (diagonally), the iPhone screen supports multitouch operation and allows a pixel resolution of 480 × 320 at 163 ppi (see Figure 1-14). When designing your application, note that despite the 480 x 320 resolution, most of the time you're limited to 460 × 320 pixels because of the status bar. Of course, you can turn off the status bar programmatically and gain access to the full 480 × 320 resolution.

Figure 1.14. Figure 1-14

Also, be mindful that users may rotate the device to display your application in Landscape mode. In that case, you have to make provisions to your user interface so that the applications can still work properly in Landscape mode should you decide to support the new orientation.

If you are new to mobile programming, you need to be aware that the limited screen real estate means that most mobile platforms support only single-window applications — that is, your application window occupies the entire screen. The iPhone is no exception to this platform limitation. Overlapping windows that are so common in desktop operating systems (such as Mac OS X and Windows) are not supported on the iPhone.

One of the major challenges in programming mobile devices is power management. A badly written application can be a resource hog and will drain the battery of the device very quickly. Apple acknowledges this issue, and from reviewing experiences obtained from other platforms, decided that major culprits in hurting battery life and performance are background applications. On other platforms (such as Windows Mobile), when an application goes out of view (because of an incoming call, for example), the application remains in memory, and each background application retained in memory continues to takes its toll on the device's performance and battery life.

Apple's solution to this problem is simple: Disallow applications to run in the background. Although this is an effective solution, it has irked a lot of developers. Many useful applications require background operation to function correctly. For example, a chatting application needs to be running to receive messages from other users. To overcome this limitation, Apple has developed its Push Notification Service, which feeds applications with data even when they are not running. This service was released with iPhone 3.0. Using push technology, a device is constantly connected to Apple's server through an IP connection. When a device needs attention, a notification is sent from Apple's server to the device, thereby alerting the specific application that needs to service that notification.

Another restriction that Apple places on iPhone developers is that you are not allowed to call third-party applications from within your application. In addition, you can't run interpreted code from within your application. A good example involves writing a Web browser application for the iPhone. Because Web applications typically use JavaScript for client-side interactivity, this restriction by Apple means that you can't run JavaScript code from within your application.