Objective-C: Count to every "tenth" in array

I was wondering how do I get sort through an do something different based on every "tenth" item in an array. I don't know much but I think it would kind of go like this...

for (NSDictionary *object in array) {

    if (0==(object % 10)) {

        //DO SOMETHING
    }

}

But this is obviously pseudo code that doesn't work. Can any one help me out with this?

Try this.

for (NSInteger i = 0 ; i < array.count ; i++)
{
    if(i%10 == 0)
    {
        // Do Something
    }
}

or

for (NSDictionary *object in array)
{
    NSInteger index = [array indexOfObject:object];
    if(index%10 == 0)
    {
        // Do Something
    }
}

Added

Assume that the array is NSArray.

NSArray *array;
NSMutableArray *tempArray = [NSMutableArray array];
for (NSInteger i = 0 ; i < array.count ; i++)
{
    if(i%10 == 0)
    {
        [tempArray addObject:/*some object*/];
    }
    [tempArray addObject:[array objectAtIndex:i]];
}
array = [NSArray arrayWithArray:tempArray];

if array was like below and add A at every 10th.

|0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|....
// 9 is the first 10th
// 19 is the second 10th

will be

|0|1|2|3|4|5|6|7|8|a|9|10|11|12|13|14|15|16|17||18|a|19....

Added

as rmaddy commented, to insert object, don't need to iterate all objects.

for (NSInteger i = 0 ; i < array.count ; i+=10)

You can use this. However you can just insert objects at index.

NSMutableArray *array;  // this is the original array;
NSArray *objects;       // this is the objects to insert array;
for(NSInteger i = 0 ; i < objects.count ; i++)
{
    [array insertObject:objects[i] atIndex:9+(i*11)];
}