Question

If I want to use a loop like

for (NSUInteger row = 10; row >= 0; row--) {
  // do something
}

how do I get around the fact that row will always be > 0 since it’s an unsigned integer. Does the middle construct of the for loop just become:

for (NSUInteger row = 10; row; row--) {

}

Answer 1

If you use NSInteger instead of NSUInteger this gets a bit simpler. Because NSInteger is a signed integer type, calling the decrement operator (--) on a variable with the value zero changes the value to -1, so you can test for this using a simple comparison:

for (NSInteger row = 10; row >= 0; row--) {
    // do stuff with row
}

If you have to use an NSUInteger for some reason then calling the decrement operator on a variable with a value of zero will result in the variable’s value wrapping around to the maximum possible value for NSUInteger. You can test for this using NSUIntegerMax.

for (NSUInteger row = 10; row != NSUIntegerMax; row--) {
    // do stuff with row
}