$source.AttributeName

I wanted to see what kinds of values you could give a value expression. I did a Google search and found some questions from people on mailing lists and message boards from people who wanted the same information as I did. But I found no answers. After doing some more searching, I learned an important piece of information.

A value expression is an object of the NSExpression class. With this information I could look at Apple’s documentation. The place to start is the NSExpression class reference. In the class reference is a link to Apple’s Predicate Programming Guide. After looking at both documents, I learned value expressions are a large topic with many possible values, too many for me to answer here. But I now know where to look when I need information on value expressions. Now you know where to look too.

For Java profiling to work with Shark, you must link Shark with the Java virtual machine. To link Shark with the Java virtual machine, you must add the following flag to the virtual machine:

-agentlib:Shark

Profiling with Shark on Snow Leopard is complicated by the fact that Snow Leopard initially uses the 64-bit version of the Java virtual machine. Shark does not work with 64-bit Java applications. You must use the 32-bit version of the Java virtual machine to profile with Shark. Add the following flag to the virtual machine

-d32

If you’re using Xcode 3.2 to write your Java applications, you must add the flags to the build.xml file Xcode includes when you create a Java project. Search build.xml for the </java> tag and add the flags before that tag.

<jvmarg value="-d32"/>
<jvmarg value="-agentlib:Shark"/>

At this point you’ll be able to use the Java Time Profile and Java Call Trace profiles. You won’t be able to use the Java Alloc Trace profile because Snow Leopard uses JVM 1.6, and the Java Alloc Trace profile doesn’t work with it. You will have to install JVM 1.5 to use Java Alloc Trace.

My workaround was to open the statistics and trace windows and start profiling. When I did this, both windows filled with the appropriate profiling data.

NOTE: The information in this post is for people writing Mac GUI applications, not games. You could write a Mac game without having to learn Objective-C and Cocoa. Getting started in game development would be a good topic for a future post.

The Tools You Need

If you have a copy of Mac OS X, you have the tools you need to write Mac applications. Apple includes developer tools, the Xcode Tools, with every copy of Mac OS X. Insert your Mac OS X DVD. The Xcode installer is in the Optional Installs folder.

Apple constantly updates their developer tools. To get the latest version of Xcode, go to Apple’s developer site. You will have to sign up for a free ADC membership before you can download Xcode.

If you’re interested in iPhone development, download the iPhone SDK instead of Xcode. The iPhone SDK contains both the Xcode Tools and the iPhone SDK. If you download Xcode, then download the iPhone SDK at a later date, you’re downloading Xcode twice, and Xcode is a large download.

After installing Xcode you will have all the tools you need to write Mac applications. The tools you will use the most are Xcode and Interface Builder.

Xcode is an integrated development environment. You will use Xcode to write your source code and compile the source code into a Mac application. You will use Interface Builder to create the user interface for your applications.

Learning a Programming Language

Before you can write Mac applications, you must know a programming language. If you have never programmed before, you will have to learn one. What language should you learn?

If you’re serious about writing Mac applications, you should eventually learn Objective-C. The Cocoa framework uses Objective-C as well as the Cocoa Touch framework, which is used to write iPhone applications.

Your First Language

Should you learn Objective-C first? If you post this question on a Mac programming message board, you will generate a lot of heated responses. These responses generally fall into three camps.

Camp 1: Learn Objective-C first. You have to know Objective-C to write Cocoa applications so you should go ahead and learn Objective-C.

Camp 2: Learn C, then Objective-C. Objective-C is a superset of C. It takes C and adds support for object-oriented programming. By learning C, you’ll make progress towards learning Objective-C.

Camp 3: Learn a language like Python or Ruby first. C and Objective-C are too difficult for a beginner. Python and Ruby are easier to learn. Start with one of them. After you learn Python or Ruby, you can move on to Objective-C.

Which camp is right? It depends on you and how you plan on learning Objective-C. If you plan on learning Objective-C through online tutorials, Camp 2 is right. Most Objective-C tutorials assume you know C so you would have to learn C first to understand the tutorials.

If you plan on learning Objective-C through Stephen Kochan’s Objective-C book (Amazon link), Camp 1 is right. The book doesn’t assume you know C so you can use the book to learn Objective-C without learning C first.

If you start learning C or Objective-C and have a hard time understanding the material, Camp 3 is right. Start with another language and learn Objective-C later.

Resources for Learning Programming

The World Wide Web is full of programming tutorials. The following sites will give you a large collection of programming language tutorials:

• CocoaDevCentral has tutorials on C and Objective-C.
• CProgramming.com has C tutorials.
• The Python website has tutorials for learning Python in the Documentation section.
• The Ruby website has Ruby tutorials in the Documentation section.

Some of you will prefer learning programming from a book. You can find books on Mac programming, Python, and Ruby from the following publishers:

• Apress
• InformIT
• O’Reilly
• Pragmatic Programmers

Three programming language books that would help someone interested in Mac programming are the following:

• Learn C on the Mac by Dave Mark.
• Learn Objective-C on the Mac by Mark Dalrymple and Scott Knaster. This book is a sequel of sorts to Learn C on the Mac and assumes you’ve read Learn C on the Mac.
• Programming in Objective-C 2.0 by Stephen Kochan.

Learning Programming on a Mac

If you’re learning C or Objective-C, you can use Xcode to learn the language. Create a command-line tool project for each program you write. In Xcode 3.2 take the following steps to create a command-line tool project:

1. Choose File > New Project in Xcode.
2. Select Application under Mac OS X on the left side of the New Project Assistant.
3. Select Command Line Tool at the top of the New Project Assistant.
4. Pick your language from the Type pop-up menu. Choose Foundation for Objective-C.
5. Click the Choose button.
6. Name your project and pick a location to save it.
7. Click the Save button.

For those of you running older versions of Xcode, create a Standard Tool project to learn C or a Foundation Tool project to learn Objective-C.

Some people think integrated development environments like Xcode hide too many details from beginning programmers, which hinders learning. They suggest beginners write their source code in a text editor and compile it from the Terminal application. For more information on compiling from the Terminal, read my Avoiding Xcode post.

If you’re learning Python or Ruby, I have good news. Mac OS X comes with Python and Ruby interpreters so you can start writing Python and Ruby programs right now. For Python and Ruby programming, I recommend using TextWrangler, which is a free text editor. You can write, run, and debug Python and Ruby programs inside TextWrangler. My TextWrangler and Interpreted Languages post has more information on using TextWrangler.

Learning Cocoa

After learning Objective-C, you can move on to learning Cocoa. Cocoa is Apple’s framework for writing GUI applications on Mac OS X. Cocoa is a large framework so prepare to spend a lot of time learning it.

Cocoa Books

When people ask for book recommendations on Mac programming message boards, the usual recommendation is Aaron Hillegass’ Cocoa Programming for Mac OS X (Amazon link). This book does a good job of teaching the fundamentals of Cocoa programming. Hillegass assumes the reader knows C so his book is not right for people completely new to programming.

Cocoa is becoming a hot topic for computer book publishers. You can find a lot of new and upcoming Cocoa books from the following publishers:

• Apress
• InformIT
• O’Reilly
• Pragmatic Programmers

Cocoa Learning Resources

The biggest source for Cocoa documentation is Apple. You can read Apple’s documentation in Xcode by choosing Help > Developer Documentation. You can also read it online at Apple’s developer site.

Some other sites that will help you learn Cocoa are:

• CocoaDevCentral, which has a lot of Cocoa tutorials.
• CocoaDev, which has lots of Cocoa information and a forum to ask questions.
• PlanetCocoa, which is a large collection of Cocoa programming blogs.
• Cocoabuilder, which contains an archive of Apple’s Cocoa mailing list.
• Andy Matuschak has a learning path for Cocoa on his blog.

This list is obviously not exhaustive. Use your favorite search engine to find more resources for learning Cocoa development and learning programming in general.

What’s the Deployment Target?

The deployment target is the earliest version of Mac OS X that can run your program. When you create an Xcode project, it sets the deployment target to the version of Mac OS X you’re using, which will be 10.5 if you’re using Xcode 3. The initial deployment target is fine if you’re writing programs for personal use, but your program won’t run if you give it to someone running an older version of Mac OS X. If you want your application to run on Leopard and Tiger, you must set the deployment target to 10.4.

In Xcode choose Project > Edit Project Settings to edit your project’s build settings. The Deployment Target build setting is in the Deployment build settings collection. If you set the deployment target to 10.4, your application will run on any Mac running Mac OS X 10.4 or higher. The previous sentence assumes your application is not using any technologies Apple introduced in Leopard, such as Core Animation.

What About the SDK?

When you installed Xcode, you installed one or more Mac OS SDKs (software development kit). The default installation of Xcode 3 installs the 10.4 and 10.5 SDKs. An SDK contains everything you need to build an application for a particular version of Mac OS X. The SDK for a particular version of Mac OS X contains the latest technologies your application can use. If you use the 10.5 SDK, your application can use Leopard technologies like toolbars created in Interface Builder and the new HID Manager APIs.

Xcode 3 projects initially use the 10.5 SDK. In most cases there is no need to change SDKs. The SDK has no effect on what versions of Mac OS X can run your program. You can use the 10.5 SDK and still support Tiger. Just set the deployment target to 10.4. By using the 10.5 SDK, your application can take advantage of any bug fixes Apple made in the 10.5 SDK. Normally the best course of action is to use the latest SDK while using the earliest deployment target you want to support.

When to Use an Earlier SDK?

Last section I said there was rarely a need to change SDKs. When would you want to use an earlier SDK? I can think of two reasons why you might want to use an earlier SDK. The first reason is if you want to build a version of your application for a specific version of Mac OS X. Suppose you had two versions of your application: one for Leopard and one for Tiger. You might want to use the 10.5 SDK for the Leopard version and the 10.4 SDK for the Tiger version.

The second reason is for testing purposes. Suppose you’re supporting Leopard and Tiger and you want to make sure you didn’t use any Leopard-specific function calls. You would temporarily use the 10.4 SDK so you could discover any compatibility errors when you build the project . Once your code compiled without any problems with the 10.4 SDK, you could switch to the 10.5 SDK. The Base SDK build setting lets you temporarily change the SDK. You could use the 10.4 SDK for the Debug build configuration and the 10.5 SDK for the Release build configuration.

Conclusion

To support earlier versions of Mac OS X, change the deployment target, not the SDK.

You change the working directory by modifying the method -setupWorkingDirectory: in the file SDLMain.m. You’ll want to change the code in SDLMain.m in SDL’s Xcode templates so your changes take effect for any new SDL projects you create. Just to be safe, you should comment out the original code or save a copy of it so you can go back to the original if things go wrong. Enter the following code in the -setupWorkingDirectory: method:

NSString *resourcePath = [[NSBundle mainBundle] resourcePath];[[NSFileManager defaultManager] changeCurrentDirectoryPath:resourcePath];

Thanks to Keith Bauer, aka OneSadCookie, for the source code to change the working directory.

To use Saturn to profile your code, you must compile your code with either the -pg compiler flag (Generate Profiling Code build setting in Xcode) or the -finstrument-functions compiler flag. The -pg compiler flag is the flag most people use, but Apple hasn’t added the support for -pg on Intel Macs yet so using the -pg flag won’t allow you to run your code with Saturn on an Intel Mac.

The solution is to use the -finstrument-functions flag to compile your code. I didn’t see an Xcode build setting for this flag so you’ll have to add the flag to the Other C Flags or Other C++ Flags build setting in Xcode.

I don’t have an Intel Mac so I can’t test this for myself, but the information came from an Apple engineer so I will assume the information is accurate.