CHAPTER 3 ■ VARIABLES
12
Declaring Variables
Variables are declared in Objective-C with their data type first, followed by a variable
name. You must declare a variable before using it. Variable names should be meaningful,
but you can name a variable anything that you want.
Here is how you would declare an integer in Objective-C:
NSUInteger numberOfPeople;
Assigning Values
You can use the assignment operator (=) to assign a value to a variable, like so:
numberOfPeople = 100;
Once you have assigned a value, you can retrieve and use that value by referencing
the variable name.
NSLog(@"The number of people is %lu", numberOfPeople);
Note ■ You may have noticed that the NSLog statement required the %lu symbol. This
symbol is called a format specifier and NSLog will use it as a placeholder to insert values in
the comma-separated list that appears right after the string. See Table 3-1 for a list of the
format specifiers that you must use with Objective-C data types.
You can also declare variables and assign values on the same line if you like.
NSUInteger numberOfGroups = 20;
Integer Types
Integers are whole numbers, so any number that doesn’t need a decimal point is an
integer. In Objective-C, integers are expressed with the data types NSInteger and
NSUInteger.
NSUIntegers are unsigned integers, which means that they can only be positive
numbers. The maximum value that an NSUInteger can take depends on the system for
which the Objective-C code is compiled. If you compile for a 64-bit Mac, the maximum
value will be 18,446,744,073,709,551,615.
For 32-bit platforms like the iPhone 5 and below, the maximum value is
4,294,967,295. You can check these numbers yourself using the NSUIntegerMax constant.
NSLog(@"NSUIntegerMax is %lu", NSUIntegerMax);
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