Objective-C Fundamentals

Summary
311
CONTINUE
The continue statement can be used as a shortcut to cause the current iteration of the
loop to be prematurely ended, in effect causing the loop condition to immediately be
reevaluated. For example, the following listing demonstrates a loop that skips over any
numbers greater than 5.
Listing B.11
Stopping the current execution of a loop early with continue
int numbers[11] = {1, 10, 0, 2, 9, 3, 8, 4, 7, 5, 6};
int n = 0, sum = 0;
do{
if (numbers[n] > 6)
continue;
sum = sum + numbers[n];
} while (n++ < 11 && sum < 15);
NSLog(@"It takes the first %d numbers to get the sum %d", n, sum);
The loop condition causes the loop to repeat while n is less than 11 (indicating the last
number in the numbers array hasn’t been passed) and the sum is currently smaller
than 15.
Each iteration through the loop adds the next number to the running sum. But
the number is first checked if it’s greater than 6, and if so, the continue statement
skips the addition and immediately processes the next number in the numbers array.
Notice the increment of the loop counter variable, n, was moved out of the loop
and into the loop condition expression. If it hadn’t been moved but instead was incremented
similarly to previous code samples, it would’ve become stuck after the first
number greater than 6 was found. In this situation, the number would’ve caused the
continue statement to be executed, skipping the rest of the statements in the loop,
but nothing would’ve incremented the value of n to cause the next iteration through
the loop to look at the next number in the array.
It’s important to also note that the break and continue statements can exit only
out of the immediate while, do, or for loop in which they’re contained. It’s not possible
to break out of multiple loops if more than one loop is nested inside of another.
B.5 Summary
Because Objective-C is a strict superset of C, it’s important to have a strong understanding
of the principles behind C before branching out to learn about the additions
Objective-C brings to the table. This appendix offers you a firm foundation on which
to start your Objective-C learning. It’s in no way a complete coverage of C-based programming,
though, and many details have been left out.
It’s clear that Objective-C owes a great debt to the C programming language. With
C-based knowledge, you can perform calculations, make decisions, and alter the flow
of execution throughout your applications. Objective-C expands upon the C foundations
with its own flavor of object-oriented extensions.