NSMutableOrderedSet NSRangeException

Question

I am getting a NSRangeException error and I can not find the error in this very basic bit of code. Can someone help correct my blindspot?

uint32_t offsetVal = 0;
int num = 100;
_offsetVals=[[NSMutableOrderedSet alloc]initWithCapacity:num+1];
for (int i=0; i<=num; i++) // note: there is 1 greater offset record than there is glyphs!
{
    CFDataGetBytes(tableData, CFRangeMake(offset,4),(UInt8*)&offsetVal);
    offsetVal=CFSwapInt32HostToBig(offsetVal);
    [_offsetVals insertObject:[NSNumber numberWithInt:offsetVal] atIndex:i];
    offset+=4;
}

Yet the app crashes with: 'NSRangeException', reason: '* -[__NSOrderedSetM setObject:atIndex:]: index 3 beyond bounds [0 .. 1]'

zachjs · Answer 1 · 2012-10-05T16:09:09.953

1

I believe your problem is hat you've set your conditional statement to i<=num which will in turn provide an index of 100 at the end of your for loop. All array-like structures start counting at 0, so replacing that condition with i < num should solve your problem.

Edit: Using [_offsetVals addObject:[NSNumber numberWithInt:offsetVal]] instead of insertObject:atIndex: has worked out.

edited Oct 05 '12 at 16:09

answered Oct 05 '12 at 15:39

zachjs

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The message from the app says its crashing on the i=3. No where near the actual limit of the NSMutableOrderedSet. But thanks for noticing the max + 1 problem! – user216661 Oct 05 '12 at 15:42
I wonder if my file is corrupted. I'm going to try to delete the file and retype it. – user216661 Oct 05 '12 at 15:44
1

You might want to try using `[_offsetVals addObject:[NSNumber numberWithInt:offsetVal]]` as you let the set handle its own index. Also, use breakpoints to figure out which exact line brings about the error, as it might have something to do with `CFDataGetBytes`. – zachjs Oct 05 '12 at 16:01
Thanks! I just tried this and it works now. Thank you. I am concerned as I want to specify the index, but I'll cross that bridge in the future. (I did use breakpoints btw. No problem with the CFData material.) If anyone can tell me why this isn't working as expected, I'd appreciate it. – user216661 Oct 05 '12 at 16:06
Well, the set is still keeping track of the index, and, in this case, it will be the exact same as if you had specified it. In either case, you were popping objects on to the end of the set. – zachjs Oct 05 '12 at 16:10

score 0 · Accepted Answer · answered Oct 06 '12 at 17:25

The issue was that a NSMutableOrderedSet regards the initial capacity as a hint rather than an instruction, so insert failed within a few because the system hadn't allocated the necessary space. From the manual (but not within the insertObject text):

"NSMutableOrderedSet objects are not like C arrays. That is, even though you may specify a size when you create a mutable ordered set, the specified size is regarded as a “hint”; the actual size of the set is still 0. This means that you cannot insert an object at an index greater than the current count of an set. For example, if a set contains two objects, its size is 2, so you can add objects at indices 0, 1, or 2. Index 3 is illegal and out of bounds; if you try to add an object at index 3 (when the size of the array is 2), NSMutableOrderedSet raises an exception."

NSMutableOrderedSet NSRangeException

2 Answers2