To properly debug and improve your apps, you need to understand what tools are available to you. One of the tools Apple ships as part of Xcode is called Instruments. Instruments contains a collection of measurement tools that help you to profile and analyze your app to debug and detect complex problems or performance bottlenecks. For example, Instruments can help you figure out whether your app is suffering from memory leaks. Tracking a memory leak without the right tools is tedious and nearly impossible. A tool such as Instruments can help you track down several possible causes for a memory leak, which can save you a lot of time.

In this chapter, we're going to look at an app named Mosaic. This app is a straightforward app that was built to demonstrate how you can profile your app. The app is very slow; the longer it's used and...