Compiling and running

 

 

Using Xcode

Xcode is a sophisticated application that enables you to easily type in, compile, debug, and execute programs. If you plan on doing serious application development on the Mac,

 

First, Xcode is located in the Developer folder inside a subfolder called Applications.

Figure 2.1shows its icon.

 

Start Xcode. Under the File menu, select New Project

 

A window appears, as shown in Figure 2.3.

 

 

 

Scroll down the left pane until you get to Command Line Utility.In the upper-righ tpane, highlight Foundation Tool. Your window should now appear as shown

 

 

Click Choose.

This brings up a new window,shown

 

Starting a new project: selecting the application type

Starting a new project: creating a Foundation tool

 

 

first program name prog1,so type that into the Save As field.

 

 

You may want to create a separate folder to store all your projects in. On my system,I keep the projects for this book in a folder called ObjC Progs.

Click the Save button to create your new project. This gives you a project window

 
 

 

Note that your window might display differently if you've used Xcode before or have changed any of its options.

 

Now it's time to type in your first program. Select the file prog1.m

in the upper-right pane.

Your Xcode window should now appear as shown

 

 

Objective-C source files use .m as the last two characters of the filename (known as its extension).

commonly used filename extensions.

Returning to your Xcode project window, the bottom-right side of the window shows the file called prog1.mand contains the following lines:

 

#import <Foundation/Foundation.h>

 

int main (int argc, const char * argv[]) {

NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

// insert code here...

NSLog (@"Hello World!");

[pool drain];

return 0;

}

 

 

Note If you can't see the file's contents displayed, you might have to click and drag up the bottom right pane to get the edit window to appear. Again, this might be the case if you've previously used Xcode.

You can edit your file inside this window. Xcode has created a template file for you to use.

Don't worry about all the colors shown for your text onscreen. Xcode indicates values,

Reserved words, and so on with different colors.

Now it's time to compile and run your first program—in Xcode terminology, it's called build and run. You need to save your program first, however, by selecting Save from the File menu.

If you try to compile and run your program without first saving your file, Xcode asks whether you want to save it.

 

Compiling and Running Programs Under the Build menu, you can select either Build or Build and Run. Select the latter because that automatically runs the program if it builds without any errors. You can also click the Build and Go icon that appears in the toolbar.

Note Build and Go means "Build and then do the last thing I asked you to do," which might be Run, Debug, Run with Shark or Instruments, and so on. The first time you use this for a project, Build and Go means to build and run the program, so you should be fine using this option. However, just be aware of the distinction between "Build and Go" and "Build and Run."

If you made mistakes in your program, you'll see error messages listed during this step.

In this case, go back, fix the errors, and repeat the process. After all the errors have been removed from the program, a new window appears, labeled prog1 – Debugger Console.

This window contains the output from your program and should look

 

 

 

 

 

 

If this window doesn't automatically appear, go to the main menu bar and select Console from the Run menu.

 

We discuss the actual contents of the Console window shortly.

You're now done with the procedural part of compiling and running your first pro-

gram with Xcode (whew!).The following summarizes the steps involved in creating a new program with Xcode:

1.Start the Xcode application.

2.If this is a new project, select File, New Project.

3.For the type of application, select Command Line Utility, Foundation Tool, and click Choose.

Select a name for your project, and optionally a directory to store your project files in. Click Save.

5.In the top-right pane, you will see the file prog1.m(or whatever name you assigned to your project, followed by .m. Highlight that file. Type your program into the edit window that appears directly below that pane.

6.Save the changes you've entered by selecting File, Save.

7.Build and run your application by selecting Build, Build and Run, or by clicking the Build and Go Button.

8.If you get any compiler errors or the output is not what you expected, make your changes to the program and repeat steps 6 and 7.

 

 

 

Using Terminal

 

 

Some people might want to avoid having to learn Xcode to get started programming with Objective-C. If you're used to using the UNIX shell and command-line tools, you might want to edit, compile, and run your programs using the Terminal application. Here we examine how to go about doing that.

The first step is to start the Terminal application on your Mac. The Terminal application is located in the Applications folder, stored under Utilities. Figure 2.9shows its icon.

Start the Terminal application. You'll see a window that looks like Figure 2.10.

You type commands after the

 

$

 

depending on how your Terminal application is configured) on each line. If you're familiar with using UNIX, you'll find this straight forward.

First, you need to enter the lines from Program

 

 

 

 

 

into a file. You can begin by creating a directory in which to store your program examples. Then you must run a text editor, such as vi or emacs, to enter your program:

 

$mkdir Progs

 

Create a directory to store programs in

 

$cd Progs

 

Change to the new directory

 

$vi prog1.m

 

Start up a text editor to enter program..

 

 

NoteIn the previous example and throughout the remainder of this text, commands that you, then user, enter are indicated in boldface.

For Objective-C files, you can choose any name you want;

just make sure the last two characters are .m.

This indicates to the compiler that you have an Objective-C program.

After you've entered your program into a file, you can use the GNU Objective-Ccompiler, which is called gcc, to compile and link your program.This is the general format of the

 

 

gcc command:gcc –framework Foundation files-o progname

 

This option says to use information about the Foundation framework:

-framework Foundation

 

Just remember to use this option on your command line.

Files is the list of files to be compiled. In our example, we have only one such file, and we're calling it prog1.m.

Prog name is the name of the file that will contain the executable if the program compiles without any errors.

 

We'll call the program prog1;here,then,is the command line to compile your first Objective-C program:

 

$gcc –framework Foundation prog1.m -o prog1

 

Compile prog1.m & call it prog1

 

The return of the command prompt without any messages means that no errors were found in the program. Now you can subsequently execute the program by typing thename prog1 at the command prompt:

 

$prog1

 

Execute prog1

 

prog1: command not found

 

 

This is the result you'll probably get unless you've used Terminal before.

 

 

The UNIX shell (which is the application running your program) doesn't know where prog1is located (we don't go into all the details of this here),

so you have two options: One is to precede the name of the program with the characters ./ so that the shell knows to look in the current directory for the program to execute. The other is to add the directory in which your programs are stored (or just simply the current directory) to the shell's PATH variable. Let's take the first approach here:

 

 

$ ./prog1

 

Execute prog1

 

2008-06-08 18:48:44.210 prog1[7985:10b] Programming is fun!

 

 

You should note that writing and debugging Objective-C programs from the terminal is a valid approach. However,it's not a good long-term strategy.

 

If you want to build MacOS X or iPhone applications,

 

there's more to just the executable file that needs to be "packaged" into an application bundle. It's not easy to do that from the Terminal

application, and it's one of Xcode's specialties. Therefore, I suggest you start learning to use Xcode to develop your programs. There is a learning curve to do this, but the effort will be well worth it in the end.