Check whether data is present at an index in NSMutableArray

Question

I have a NSMutableArray, I want to insert data inside it, the problem is first I want to check if the index where I'm inserting the data exists or not. How to do that? I try something like that but nothing is working:

if ([[eventArray objectAtIndex:j] count] == 0)

or

if (![eventArray objectAtIndex:j])

score 11 · Accepted Answer · answered Feb 26 '10 at 08:41

11

if (j < [eventArray count])
{
     //Insert
}

answered Feb 26 '10 at 08:41

willcodejavaforfood

43,223
17
81
111

Doesn't answer the OP's question; ludo is looking for something akin to a sparse array. – bbum Feb 26 '10 at 08:48
1

I'm stupid sometimes -,.- anyway thanks for this fast answer~ ^^ – ludo Feb 26 '10 at 08:55
no no it's working perfectly, I didn't even think of that easy one haha – ludo Feb 26 '10 at 08:56

score 3 · Answer 2 · edited Jun 03 '13 at 07:24

NSArray and NSMutableArray are not sparse arrays. Thus, there is no concept of "exists at index", only "does the array have N elements or more".

For NSMutableArray, the grand sum total of mutable operations are:

- (void)addObject:(id)anObject;
- (void)insertObject:(id)anObject atIndex:(NSUInteger)index;
- (void)removeLastObject;
- (void)removeObjectAtIndex:(NSUInteger)index;
- (void)replaceObjectAtIndex:(NSUInteger)index withObject:(id)anObject;

All other mutability methods can be expressed in terms of the above and -- more specifically to your question -- removing an object does not create a hole (nor can you create an array with N "holes" to be filled later).

This does not answer the OP's question :P – willcodejavaforfood Feb 26 '10 at 09:00 — willcodejavaforfood, Feb 26 '10 at 09:00

score 0 · Answer 3 · edited May 23 '17 at 12:13

0

I've given a brief implementation of a sparse array in this question: Sparse Array answer

edited May 23 '17 at 12:13

Community

1
1

answered Jun 24 '11 at 13:49

Jane Sales

13,526
3
52
57

Check whether data is present at an index in NSMutableArray

3 Answers3