iPhone® Application Development All-In-One For Dummies®

Chapter 2. Tuning Your Code Using Xcode's Instruments Application

In This Chapter

• Measuring application performance

• Finding memory leaks

• Keeping in mind that the Simulator is not the device

• Hunting down zombies

Yogi Berra, in my humble opinion, is one of the great philosophers of all time. I'm sure he was talking about application development when he said, "It ain't over till it's over." So even if you've successfully compiled and launched your app and it seems to run (correctly), there's still work you need to do.

Before you attempt to get your application into the App Store or even run it on anyone's iPhone, you need to make sure it's behaving properly. By that I mean not only delivering the promised functionality, but also avoiding the unintentional misuse of iPhone resources. Keep in mind that the iPhone, as cool as it may very well be, is nevertheless somewhat resource-constrained when it comes to memory usage and battery life. Such restraints can have a direct effect on what you can (and can't) do in your application. Xcode's Instruments application lets you know how your application uses iPhone resources such as the CPU, memory, network, and so on.

The Instruments application allows you to observe the performance of your application while running it on the IPhone, and to a lesser extent, while running it on the Simulator. Here, instrument means a specialized feature of the Instruments application that zeroes in on a particular aspect of your app's performance (such as memory usage, ...