Adding sections to tableview, index out of bounds error - ios

Question

In this app, I download data from Parse. That data is a list of 5 Messages, each with a category. There are 4 different categories as two of the messages have the same category. I want to put that data into sections on a tableview. Since the data is not ready for sectioning, I had to create 2 mutable arrays that act like index look ups. (followed this guide: https://parse.com/questions/using-pfquerytableviewcontroller-for-uitableview-sections)
Problem: I'm getting this error:
-[__NSArrayM objectAtIndex:]: index 8 beyond bounds [0 .. 4]'
Question is, why am I getting this error and how do I fix it?
I've located the exact line that is the problem. First, here is what you need.
1st Mutable Dictionary:
self.sectionToCategoryMap //This property maps the sections titles to the row indeces for the data. The output it looks like this: (read as, get the 1st category header from object at index 0)
0 = "Section Header 1";
24 = "Section Header 2";
16 = "Section Header 3";
32 = "Section Header 4";
2nd Mutable Dictionary:
self.sections // This maps what items are in what section(category). Output looks like this:
"category 1" =(32);
"category 2" =(24);
"category 3" =(16);
"category 4" =(0,8);
These two Dictionaries are created by this code:
- (void)prepSections:(id)array {
[self.sections removeAllObjects];
[self.sectionToCategoryMap removeAllObjects];
self.sections = [NSMutableDictionary dictionary];
self.sectionToCategoryMap = [NSMutableDictionary dictionary];
NSInteger *section = 0;
NSInteger *rowIndex = 0;
for (MessageItem *messageItem in self.messageList) {
NSString *category = [messageItem valueForKey:#"messageCategory"]; //retrieves category for each message -1st regulator
NSMutableArray *objectsInSection = [self.sections objectForKey:category]; //assigns objectsinsection value of sections for current category
if (!objectsInSection) {
objectsInSection = [NSMutableArray array];
// this is the first time we see this category - increment the section index
//literally it ends up (0:Regulatory)
[self.sectionToCategoryMap setObject:category forKey:[NSNumber numberWithInt:rowIndex]];
section++;
}
[objectsInSection addObject:[NSNumber numberWithInt:(int)rowIndex++]]; //adds message to objects in section
[self.sections setObject:objectsInSection forKey:category]; //adds dict of objects for category
}
}
The error is happening in my in cellForRowAtIndexPath below, specifically the line:
NSNumber *rowIndex = [rowIndecesInSection objectAtIndex:indexPath.row];
(note: categoryForSection is a helper method I defined, its implementation is also below.)
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
MessageTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
NSString *category= [self categoryForSection:indexPath.section];
NSArray *rowIndecesInSection = [self.sections objectForKey:category];
NSNumber *rowIndex = [rowIndecesInSection objectAtIndex:indexPath.row]; //pulling the row indece from array above
//gets to 3 and breaks!!!
messageItem = [self.messageList objectAtIndex:[rowIndex intValue]];
[cell configMessageCell:messageItem indexPath:indexPath];
return cell;
}
For good measure, here is the rest of my code.
- (NSString *) categoryForSection:(NSInteger*)section { //takes section # and returns name of section.
return [self.sectionToCategoryMap objectForKey:[NSNumber numberWithInt:(int)section]];
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return (unsigned long)self.sections.allKeys.count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
NSString *category = [self categoryForSection:section];
NSArray *rowIndecesInSection = [self.sections objectForKey:category];
return [rowIndecesInSection count];
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
NSString *category =[self categoryForSection:section];
return category;
}
Please help me fix this. It has had me stuck for days! Thank you!
Matt

Answer 1

I think the problem lies in declaring these as pointers:
NSInteger *section = 0;
NSInteger *rowIndex = 0;
(Note the weird multiples of 8 in the numbers in your dictionaries - that's because pointer arithmetic works differently from "normal" arithmetic). Try with
NSInteger section = 0;
NSInteger rowIndex = 0;