Is there an easy method to check is an NSRange passed to substringWithRange on NSString exists (so not to cause an error)?

Question

Say I pass the NSRange of (location: 5, length: 50) on the NSString "foo", that range obviously doesn't exist.

Is there a way to say [string rangeExists:NSRange] for instance, or do we have to manually validate the input?

Answer 1

You have to write your own check but it's simple enough:

NSString *str = ... // some string
NSRange range = ... // some range to be used on str

if (range.location != NSNotFound && range.location + range.length <= str.length) {
    // It's safe to use range on str
}

You could create a category method on NSString that adds your proposed rangeExists: method. It would just be:

- (BOOL)rangeExists:(NSRange)range {
    return range.location != NSNotFound && range.location + range.length <= self.length;
}