Get index of object in array to look up corresponding object in other array

Question

I have two arrays. One is an array of names and the other is an array made up of strings titled "Yes" or "No". The index path of each name in the "name" array corresponds with the same index path in the "Yes/No" array. For example:

Names Array | Yes/No Array
Person 1    | Yes
Person 2    | No
Person 3    | Yes

What would be the easiest way to look up a person's name (possibly getting the index path of it) and check whether they are "Yes" or "No" in the "Yes/No" array?

Also, I'm not sure if "index path" is the right term to use. If it isn't, I mean the number that an object is in an array.

Answer 1

NSArray has a method called indexOfObject that will return either the lowest index whose corresponding array value is equal to anObject or NSNotFound if no such object is found. If your array of names is unsorted, then use this to get the index that you can then plug in to the Yes/No array. That is, something along these lines:

NSString *answer = nil;
NSUInteger index = [namesArray indexOfObject:@"John Smith"];
if (index != NSNotFound) {
    answer = [yesNoArray objectAtIndex:index];
}
return answer;

Because Bavarious asks questions where I assume, here's a better way when the array of names is sorted alphabetically.

int index = [self findName:@"John Smith"];
NSString *answer = nil;
if (index >= 0) {
    answer = [yesNoArray objectAtIndex:index];
}
return answer;

where the function findName is a simple binary search:

-(int)findName:(NSString *)name {
    int min, mid, max;
    NSComparisonResult comparisonResult;
    min = 0;
    max = [namesArray count]-1;
    while (min <= max) {
        mid = min + (max-min)/2;
        comparisonResult = [name compare:[namesArray objectAtIndex:mid]];
        if (comparisonResult == NSOrderedSame) {
            return mid;
        } else if (comparisonResult == NSOrderedDescending) {
            min = mid+1;
        } else {
            max = mid-1;
        }
    }   
    return -1;  
}