Objective-C Fundamentals

54 CHAPTER 2 Data types, variables, and constants
The tableView:numberOfRowsInSection: implementation isn’t notable. It returns
the number of items present in the properties array (5). It makes use of a C preprocessor
macro defined in listing 2.4 to determine this number, but more about that later.
The tableView:cellForRowAtIndexPath: implementation has a couple of changes.
The first is a change in table view cell styles. You’re now requesting UITableViewCell-
StyleSubtitle, which provides an iPod application–style cell with two horizontal
lines of text: a main one that’s black followed by a gray line designed to show additional
details.
In tableView:cellForRowAtIndexPath: you’re provided with the index of the row
the UITableView wants data for via the indexPath.row property. You can use this
expression to index into the properties array to access the details, such as the
address, of the associated property. Likewise, you can format a similar string detailing
the rental price of the property to two decimal places for use as the details line.
Build and run the application (Cmd-R), and you should be rewarded with a much
better list of rental properties. Your first practical version of the Rental Manager application
is completed!
2.6 Summary
All software applications are ultimately about data and how to interpret, process, and
present it to the user. Even games are required to store maps, enemy positions, and
scoring information, for example. It’s important to have a strong grasp of how to represent
and store data in your applications.
In this chapter, you met some of the most basic data types available to Objective-C
developers, including int, float, char, and bool. We also highlighted some of the
potential issues these data types could throw up, such as the inability of floating-point
numbers to accurately represent all values in their stated ranges.
As programs start to develop and grow in complexity, managing a large number of
individual variables becomes untenable, so we investigated a number of Objective-C
features such as enumeration, structures, and arrays that allow you to group multiple
fields and constants.
In chapter 3, we complete our coverage of Objective-C data types by discussing the
concept of objects. Objects are another form of data type, but clearly, because
Objective-C begins with the word object, understanding them is fairly critical to the success
use of Objective-C.