Getting Started with Code Analysis and Debugging - Xcode 4 - page 413

Expressions can be challenging but powerful. The syntax required to display a certain value or property can be-
come complex, and you often need to rely on trial and error before you find the correct answer. But if you can
master expressions, you can make your debugging sessions significantly more productive. You can review the
most important properties and variables at a glance, without having to open other objects to reveal them.
FIGURE 15.15
Creating a custom expression to display a value of interest
Using data formatters
Every item that appears in the Variables View is formatted, and the formatting information is set by a data
formatter. All the standard data types have predefined formatters. In practice, these define extra details that
may be unnecessary. Uncheck the Enable Data Formatters option in the right-click contextual menu to hide
these details, leaving a shorter summary of the key information.
You can also customize the formatting for certain data types. Use the Edit Summary Format option to display a
dialog box with an editable field that defines the formatting. Formatters are similar to expressions, but the syn-
tax is more complex and more general. A formatter is enclosed between curly brackets and usually includes a
type cast. It may also include one or more macro placeholders to represent input data and a format reference
that selects one of four display options. Table 15.2 summarizes the key options.