iOS 5 Programming Cookbook

1.22. Allocating and Making Use of Numbers

Problem

You need to use integral values or encapsulate numbers in objects.

Solution

Use NSNumber for an object-oriented approach to handling numbers. If you require simple numbers (non-objects), use NSInteger to hold signed (positive and negative) values, NSUInteger to hold unsigned (only positive or zero) values, and CGFloat and double to hold floating point values.

Discussion

Just as we place strings inside instances of NSString, we can place numbers inside instances of NSNumber. Why, you might ask? The answer is simple: to allow an object to carry the value of our numbers so that we can save this value to disk easily, load it from disk, and simply allow a single object to carry signed and unsigned integral and floating point values, without the need for typecasting or defining multiple variables. The possibilities are virtually endless.

Let’s have a look at constructing instances of NSNumber:

NSNumber *signedNumber = [NSNumber numberWithInteger:-123456];
NSNumber *unsignedNumber = [NSNumber numberWithUnsignedInteger:123456];
NSNumber *floatNumber = [NSNumber numberWithFloat:123456.123456f];
NSNumber *doubleNumber = [NSNumber numberWithDouble:123456.1234567890];

Just as we placed signed and unsigned integers and floating point values into an instance of NSNumber class, we can retrieve those values back using some really handy instance methods of NSNumber class, as shown here:

NSNumber *signedNumber = [NSNumber numberWithInteger:-123456]; NSNumber ...