How can I decode an NSString using the A1Z26 cipher?

Question

I'm trying to decode an using the A1Z26 cipher (which is just a=1, b=2, ..., z=26). The input text is separated by hyphens, like this:

-8-16-2-7-8-5-

I have JavaScript which solves this problem, but I cannot seem to get a version working in Objective C

function a1z26Cipher(inputString) {
    var outputString = "";
    var splitString = inputString.split(/(\W| )/);
    for (var i = 0; i < splitString.length; i++) {
        var n = splitString[i];
        if (n >= 1 && n <= 26) outputString += String.fromCharCode(parseInt(n, 10) + 64);
        else outputString += n.replace("-", "");
    }
    return outputString;
}

What would equivalent code in Objective C look like?

Answer 1

In Objective C this can be done as follows:

-(NSString *)decode:(NSString *)input {
    NSArray<NSString *> *components = [input componentsSeparatedByString:@"-"];
    NSMutableString *output = [[NSMutableString alloc] init];
    for (NSString *component in components) {
        if (component.length == 0) {
            continue;
        }
        char charValue = (char) [component intValue];
        [output appendFormat:@"%c", charValue + ('a' - 1)];
    }
    return [NSString stringWithString:output];
}

Note that this assumes the input already has the correct format. It will accept strings of the form "--42-df-w---wf" happily.

EDIT: If there are multiple possible separators (e.g. hyphen and space), you can use NSCharacterSet:

-(NSString *)decode:(NSString *)input {
    NSCharacterSet *separatorSet = [NSCharacterSet characterSetWithCharactersInString: @"- "];
    NSArray<NSString *> *components = [input componentsSeparatedByCharactersInSet:separatorSet];
    ...
}