Objective-C place object into each array

Question

I am a newbie to Objective-C and iOS.

I have a NSMutableArray with 180 objects.They are all sorted.

NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity:180];
for (int i = 0; i < 180; i ++) {
    NSString *string = [NSString stringWithFormat:@"%d",i+1];
    [array addObject:string];
}

Now, I want to put them into a NSArray, which this NSArray is a five-objects Array.(I mean the array contains 5 object each). And I had come up with two method to do so.

Method 1

NSMutableArray *outer = [[NSMutableArray alloc] init];
NSMutableArray *inner =  [[NSMutableArray alloc] initWithCapacity:5];
for (id object in array)
{
    int i = 0;
    [inner addObject:object];
    if (i % 5 == 0) {
        [outer addObject:inner];
    }
    i ++;
}
NSLog(@"%@",outer);

Method 2

NSMutableArray *outer = [[NSMutableArray alloc] init];
NSMutableArray *inner =  [[NSMutableArray alloc] initWithCapacity:5];
for (int i = 0; i < 180; i ++)
{
    if (i % 5 == 0 && i != 0) {
        [outer addObjectsFromArray:inner];
        [inner removeAllObjects];
        [inner addObject:array[i]];
    }else{
        [inner addObject:array[i]];
    }
}
NSLog(@"%@",outer);

How can I do that? Thanks in advance.

You are modifying the same object which is inner array over and over and storing it in outer array instead create new inner array every time when limit which is 5 is exhausted. — dev gr
– dev gr, Commented Jan 3, 2015 at 13:20

ZeMoon · Accepted Answer · 2015-01-03 10:48:28Z

2

You were on the right track with the first approach, which is simplest.

However, there were a few problems:

i was being set to 0 each time. It needs to be declared outside.

NSMutableArray *outer = [[NSMutableArray alloc] init];
NSMutableArray *inner = nil;
int i = 0;

for (id object in array)
{
    if (inner = nil) {
        inner = [[NSMutableArray alloc] init];
    } 
    [inner addObject:object];
    i ++;
    if (i % 5 == 0) {
        [outer addObject:inner];
        inner = nil;
        i = 0;
    }
}

answered Jan 3, 2015 at 10:48

ZeMoon

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Comments

Abhishek Sharma · Accepted Answer · 2015-01-03 11:25:58Z

1

- (NSArray *)Addarraydata : (NSMutableArray *) inputArray{

    NSMutableArray * arrNewArray = [NSMutableArray array];

    for(int i = 0; i < [inputArray count]; i = i + 5){
        if((i + 5) < [inputArray count]){
           [arrNewArray addObject:[inputArray subarrayWithRange:NSMakeRange(i, 5)]];
        }else{
            [arrNewArray addObject:[inputArray subarrayWithRange:NSMakeRange(i, ([inputArray count] - i))]];
        }
    }

    NSLog(@"arrNewArray = %@",arrNewArray);

    return arrNewArray;
}

edited Jan 3, 2015 at 11:25

answered Jan 3, 2015 at 11:18

Abhishek Sharma

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Comments

Frédéric T. · Accepted Answer · 2015-01-03 18:33:05Z

0

NSMutableArray *outer = [[NSMutableArray alloc] init];

for (int i = 0; i < [array count] / 5; i++) {
   [outer addObject:[array subarrayWithRange:NSMakeRange(i*5, 5)]];
}

And if array can be a non multiple of 5 and you want to get the rest, you can add this after the for loop :

NSUInteger rest = [array count] % 5;
if (rest != 0) {
   [outer addObject:[array subarrayWithRange:NSMakeRange([array count] / 5 * 5, rest)]];
}

edited Jan 3, 2015 at 18:33

answered Jan 3, 2015 at 13:28

Frédéric T.

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1 Comment

Paul.s Over a year ago

Your for loop is invalid and will never terminate

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