Objective-C Fundamentals

304 APPENDIX B The basics of C
}
case South:
NSLog(@"We are heading south");
break;
case East:
NSLog(@"We are heading east");
break;
case West:
NSLog(@"We are heading west");
break;
default:
NSLog(@"We are heading in an unknown direction");
Comparing listing B.1 to listing B.3, you can see that the different syntax and the
amount of whitespace makes a clear impact on the readability and maintainability
of such a statement. One thing worth noticing with switch statements is that
they’re an exception to the general rule that multiple statements must be enclosed
in a set of curly braces. In each case block, it’s possible to simply list multiple statements
one after another, and they’ll all be executed in sequence if their case value
is a match.
In listing B.3 the end of each case block is punctuated by the break keyword,
which signals the end of a particular case block and causes execution to jump to the
end of the entire switch statement. The break keyword is optional; if it isn’t present,
execution follows down into the next statement even if that statement is part of
another case block. This feature is commonly used if you want to handle multiple
potential values in the same or a similar manner. As a somewhat contrived example,
take a look at the following listing.
Listing B.4
switch statement with case statements falling into each other
enum { Horse, Pony, Cat, Kitten } pet = Kitten;
switch (pet)
{
case Kitten:
NSLog(@"This is a young cat so turn on the fire");
// Falls through
case Cat:
NSLog(@"Cats can sleep inthe living room");
break;
}
case Horse:
case Pony:
NSLog(@"These pets don't belong inside the house!");
break;
The code is straightforward in the case of the pet variable storing the value Cat or
Pony. For both values, the switch statement executes the matching calls to NSLog and
then jumps to the end of the switch statement via the break keyword.