Question

I am trying to create a multiple choice test app. I have this code to read off a .txt file:

filePath = [[NSBundle mainBundle] pathForResource:@"testBank" ofType:@"txt"];
theBank = [[NSString alloc] initWithContentsOfFile:filePath
                                                  encoding:NSUTF8StringEncoding error:NULL];        
multipleChoicePractice = [theBank componentsSeparatedByString:@"\n"];

The multipleChoicePractice NSMutableArray now contains a bunch of NSStrings in this order:

 Question 1
 choice A
 choice B
 choice C
 choice D
 Answer Key
 Rationale
 question ID 1
 [string to id type of question]
 [space 1]
 Question 2
 choice A-2 
 etc etc up to Question 10

I am trying to group each index in groups of 10 so that index 0 to 9 of multipleChoicePractice is index 0 of a new mutable array, questionGroupArary. I tried:

for (i=0; i<=90; i = i+10) { //qArr being a NSMutableArray
            [qArr addObject:[multipleChoicePractice objectAtIndex:i]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+1)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+2)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+3)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+4)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+5)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+6)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+7)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+8)]];
            [qArr addObject:[multipleChoicePractice objectAtIndex:(i+9)]];

            [questionGroupArray addObject:qArr];
        }

The result of that for loop is that questionGroupArray objectAtIndex: 0 contains EVERYTHING between question 1 and question 10. What is the best way to achieve my goal so that questionGroupArray index 0 contains “question1” to “[space 1]”? I feel like there is a way to do this with a for loop but it escapes me. Thanks!

Answer 1

A much better way to get a subarray of objects in a consecutive range is to use -[NSArray subarrayWithRange:].

// Source is your ungrouped array
NSMutableArray* groups = [NSMutableArray array];
for (int i = ; i < 90; i += 10) {
    NSArray* sub = [source subarrayWithRange:NSMakeRange(i, 10)];
    [groups addObject:sub];
}
// groups is now an array of arrays with your groups.