split NSArray in groups of smaller NSArrays for paging

Question

I have an NSArray of say 100 NSManagedObjects and I need to split that into an NSArray that contains 10 NSArray objects that each hold 10 of theses NSManagedObjects, how would I accomplish that?

I am going to do some paging and this will work well for me.

Assuming you just would like to pass in an array and have the same code work every time, why not just pass it an NSRange of length 10 and position [whichever], along with the original unmodified NSArray, and have the code for a page work based on the NSRange, instead of absolute index? — Alex Gosselin, Jul 29 '11 at 00:24
This is almost an exact duplicate of http://stackoverflow.com/questions/6852012/what-is-an-easy-way-to-break-an-nsarray-with-4000-objects-in-it-into-multiple-ar. The answer was to use `subArrayWithRange:` repeatedly, with a shifting range. — Rudy Velthuis, Jul 29 '11 at 00:42

score 5 · Answer 1 · answered Jul 29 '11 at 00:41

5

How are you getting these NSManagedObjects? If you're using an NSFetchRequest, you may want to keep that around and only get 10 results at a time from it.

answered Jul 29 '11 at 00:41

Joe Osborn

1,145
7
10

score 3 · Answer 2 · answered Nov 01 '13 at 09:36

Here is my code:

[object splitArrayWithArray:arrayWith100Objects rangeNumber:10];

- (NSArray*) splitArrayWithArray:(NSArray*)rawArray rangeNumber:(int)rangeNumber{
    int totalCount = rawArray.count;
    int currentIndex = 0;

    NSMutableArray* splitArray = [NSMutableArray array];

    while (currentIndex<totalCount) {
        NSRange range = NSMakeRange(currentIndex, MIN(rangeNumber, totalCount-currentIndex));
        NSArray* subArray = [rawArray subarrayWithRange:range];
        [splitArray addObject:subArray];
        currentIndex +=rangeNumber;
    }
    return splitArray;
}

score 2 · Accepted Answer · answered Jul 29 '11 at 00:55

Something along these lines should work instead of breaking it into separate arrays

//make a new range for each page
NSRange myRange = NSMakeRange(10, 10);
NSArray * myArray = [NSArray array];

//...pass both into a function
for (int i = myRange.location; i < myRange.location + myRange.length; i++) {
    //stuff with the array elements
    [[myArray objectAtIndex:i] doSomething];
}

score 1 · Answer 4 · answered Sep 14 '13 at 20:21

It's no one-liner, but this will split an array into pages:

NSArray *arrayToSplit = ...

int pageSize = 50;
NSMutableArray *arrayOfPages = [NSMutableArray new];

NSRange range = NSMakeRange(0, pageSize);

while (range.location < arrayToSplit.count) {
    if (range.location + range.length >= arrayToSplit.count)
        range.length = arrayToSplit.count - range.location;

    [arrayOfPages addObject:[arrayToSplit objectsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:range]]];

    range.location += range.length;
}

split NSArray in groups of smaller NSArrays for paging

4 Answers4