iPhone SDK 3 : SDK and IDE Basics

In this section, we walk you through the process of creating your first iPhone application. But first, you need to obtain the iPhone SDK and install it on your Mac.

1. Obtaining and installing the SDK

Obtaining and installing the iPhone SDK is easy; just follow these steps:

Now, you're ready to create your first project – read on!

2. Creating a project

Locate XCode and launch it. You can use Spotlight to find it or you can navigate to /Developer/Applications/XCode. XCode is the central application for writing, designing, debugging, and deploying your iPhone applications. You will use it a lot, so go ahead and add it to the Dock.

From XCode, select File->New Project. You should see a window, similar to the one shown in Figure 1, asking you for the type of project you want to create. Choose the default and create a window-based application. This is the most generic type of iPhone project and the one that can be customized for different needs.

Figure 1. Choosing window-based application in the project creation process.

Click on Choose... and enter the name of your project (here, we're using My Project) and hit Save. A new directory is created with the name you entered, and several files are generated for you. You should now see the newly created iPhone project as in Figure 2.

Figure 2. A newly created iPhone project in XCode.

3. Familiarizing yourself with the IDE

As you can see from Figure 2, the main window is divided into several areas. On the top, you will find the Toolbar (Figure 3). The Toolbar provides quick access to common tasks. It is fully configurable; you can add and remove tasks as you want. To customize the Toolbar, Control-click it and choose Customize Toolbar.... There, you can drag your favorite task on the Toolbar. Hit Done when you're finished. To remove an item, Control-click on it and choose Remove Item.

Figure 3. The XCode Toolbar.

On the left-hand side, you'll see the Groups & Files list (Figure 4).

Figure 4. The Groups & Files list in XCode.

This list is used to organize the source code, frameworks, libraries, executables, and other types of files in your project.

The list shows several files and groups. Groups can contain other groups and files. You can delete a group as well as create a new one. The group indicated by the blue icon whose name is the same as the name you've chosen as the project name is a static group. Underneath it, you see all your headers, implementations, resources (images, audio files, etc.), and other related files. The folder-like yellow groups act conceptually as containers. You can have containers inside other containers and all files inside these containers live in the same directory on the disk. The hierarchy only helps you organize things. You have full freedom to organize your project's layout as you like. The compiler will pick up the resources, headers, and implementation files when it builds your application.

The other kind of groups that are listed below the project group are called smart groups. There are two types of smart groups: 1) built-in smart groups, and 2) custom smart groups. The content of the built-in smart groups cannot be customized. Examples of these groups include executables, bookmarks, errors/warnings, and targets. Customized smart groups are shown in purple, and two predefined groups are created for you when you create a new project.

Figure 5. The Details view with the text editor view.

Figure 5 shows the Details view and the text editor beneath it.

Selecting an item in the Groups & Files list will result in its details being shown in the Details view. You can go to a full-editor window using Command-shift-E.

4. Looking closely at the generated code

Expand the Classes and Other Sources groups. You will notice several files that live underneath these two groups. Click on the main.m file and expand to a full-editor view.

The main.m file looks very similar to a C file with a main() function. All that main() does is prepare for memory management and launch the application.

Click on the My_ProjectAppDelegate.h file under the Classes group. You will notice that the editor changes its content. This file contains the declaration of the application delegate class. Every application that runs on the iPhone OS has a delegate object that handles critical phases of its lifecycle.

Click on My_ProjectAppDelegate.m. This file with the .m extension is the counterpart of the previous .h file. In it, you see the actual implementation of the application delegate class. Two methods of this class are already implemented for you. The applicationDidFinishLaunching: method is one of those methods that handles a particular phase of the application lifecycle. The other method, dealloc, is a method where memory used by this object is released. In iPhone OS, you manage the allocation and freeing of memory as there is no garbage collection. Memory management is crucial in iPhone development, and mastering it is very important.