How to create a subarray of NSArray using NSRange?

Question

I have an Array with content. as usual it contain 20 objects. I want the same array split into 2 sections in Tableview. I am trying to implement it with NSMake in current array. For example I need get in first tableview section 3 rows and second will contain all the rest (17 rows ).

switch (section) {
        case 0:
            return
            [[array subarrayWithRange:NSMakeRange(3, 8)] count];
            // in this line, it always takes from the first object in array, despite I told hime start from 3 (If I understand right, how to works NSMakeRange)
            break;
        case 1:
            return
            [[array subarrayWithRange:NSMakeRange(9, 19)] count];
            // here my app is crashing with an error 
            //*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSArray subarrayWithRange:]: range {9, 19} extends beyond bounds [0 .. 19]'
        default:
            break;
    }

Does anyone can help me with that?

Answer 1

NSMakeRange is defined as (startingIndex, length), not (start, end) which it seems like how you are trying to use it.

So if you need the first 3 objects, then the rest it would look like this:

switch (section) {
    case 0:
        // This returns objects 0-2 in the array
        return [array subarrayWithRange:NSMakeRange(0, 3)];
    case 1:
        // This returns objects 3-20 in the array
        return [array subarrayWithRange:NSMakeRange(3, 17)];
    default:
        break;
}

Edit: According to your comment, you are actually looking for the count to return in number of rows in section. Since you are using a fixed number of rows, you can just return the actual number within the case statement.

switch (section) {
    case 0:
        // This returns the count for objects 0-2 in the array
        return 3;
    case 1:
        // This returns the count for objects 3-20 in the array
        return 17;
    default:
        break;
}

You do not actually need to use [subarrayWithRange], nor NSMakeRange. If you do need to at some point reference the actual array, you will get an NSIndexPath object which you can use to get the object from your array. You will need to use the section and row properties.

Edit: NSRange -> NSMakeRange