UITableView gets Slower with every new NSMutableArray - ios

Question

I have a UITableView that populates the results of a search that the user looks up. In order to do this I am using a NSMutableArray of Dictionaries where objects are added for the first 10, and then when the user scrolls to the bottom it populates the next 10 until there are no results left to show.
This all works well and good but I started to notice that the more searches that are done, the slower the table gets. Here is some of the code:
- (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar
{
[self.objectsArray removeAllObjects];
[self.objectsArray setArray:nil];
[itemsTable reloadData];
[itemsTable scrollRectToVisible:CGRectMake(0, 0, 0, 0) animated:false];
[self loadItemsFromURL:searchURL withItemDescription:encodedString atStartRow:start andEndRow:end];
}
The above is when a new search is performed. It then does a NSURLConnection and responds with this:
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
if (self.objectsArray == nil)
self.objectsArray = [NSMutableArray array];
// self.objectsArray = [[NSMutableArray alloc] init];
NSError *error;
NSDictionary *returnArray = [[NSJSONSerialization JSONObjectWithData:itemsData options:kNilOptions error:&error] valueForKey:#"items"];
for (id key in returnArray)
{
[self.objectsArray addObject:[returnArray objectForKey:key]];
}
counter += 10;
[itemsTable reloadData];
}
As you can see, if a user conducts a new search all objects are removed with [self.objectsArray removeAllObjects]and I even try to set the array to nil. If I perform multiple searches the UITableView gets slower and slower with scrolling each time. It is almost like the controller sees the array as getting larger and larger with each search even though I am removing all of the objects from it before the search. Any ideas or am I going about this the wrong way?
EDIT:
Here is the cellForRowAtIndexPath: method. cell is a subclassed UITableViewCell.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Product Cell";
static NSString *LoadCellIdentifier = #"Loading Cell";
cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if ([self.objectsArray count] <= 0 )
{
cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
cell.itemName.text = #"No items found.";
cell.itemPrice.text = #"";
cell.itemLocation.text = #"";
cell.addButton.hidden = YES;
}
else
{
if ([indexPath row] == [self.objectsArray count])
{
if ( [self.objectsArray count] >= 10 )
{
if ( [self.objectsArray count] < counter)
{
cell = [tableView dequeueReusableCellWithIdentifier:LoadCellIdentifier];
[cell.loadingSpinner stopAnimating];
cell.itemName.text = #"No more items found.";
}
else
{
if (!running)
{
[self loadItemsFromURL:searchURL withItemDescription:encodedString atStartRow:[self.objectsArray count] + 1 andEndRow:[self.objectsArray count] + 10];
cell = [tableView dequeueReusableCellWithIdentifier:LoadCellIdentifier];
cell.itemName.text = #"Loading more items...";
[cell.loadingSpinner startAnimating];
running = true;
}
else
{
cell = [tableView dequeueReusableCellWithIdentifier:LoadCellIdentifier];
[cell.loadingSpinner startAnimating];
}
}
}
}
else
{
cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
NSArray *match = [self.objectsArray objectAtIndex:[indexPath row]];
cell.addButton.hidden = NO;
if ([match valueForKey:#"DESCRIPTION"] == [NSNull null] )
{
cell.itemName.text = #"Description not available.";
}
else
{
cell.itemName.text = [match valueForKey:#"DESCRIPTION"];
}
if ([match valueForKey:#"AD"] != [NSNull null])
{
NSMutableString *adString = [NSMutableString stringWithString:[match valueForKey:#"AD"]];
NSRange textRange;
textRange = [adString rangeOfString:#"1/"];
if (textRange.location != NSNotFound)
{
[adString replaceCharactersInRange:[adString rangeOfString:#"1/"] withString:#"$"];
}
else
{
[adString replaceCharactersInRange:[adString rangeOfString:#"/"] withString:#"/$"];
}
cell.itemPrice.text = adString;
}
else if ([match valueForKey:#"REGULAR"] == [NSNull null])
{
cell.itemPrice.text = #"$ N/A";
}
else
{
NSNumberFormatter *currencyStyle = [[NSNumberFormatter alloc] init];
[currencyStyle setFormatterBehavior:NSNumberFormatterBehavior10_4];
[currencyStyle setNumberStyle:NSNumberFormatterCurrencyStyle];
NSNumber *price = [NSNumber numberWithDouble:[[match valueForKey:#"REGULAR"] doubleValue]];
NSString *stringPrice = [currencyStyle stringFromNumber:price];
cell.itemPrice.text = [NSString stringWithFormat:#"%#", stringPrice];
}
if ([match valueForKey:#"AISLE"] == [NSNull null])
{
cell.itemLocation.text = #"Item location: N/A";
}
else
{
cell.itemLocation.text = [NSString stringWithFormat:#"Item Location: %#", [match valueForKey:#"AISLE"]];
}
match = nil;
}
}
return cell;
}
EDIT 2:
Here is a snippet of what the JSON looks like:
{
items = {
263149 = {
AD = "###";
AISLE = 6A;
DESCRIPTION = "Cinnamon Toasters";
R = 9;
REGULAR = "#.##";
};
26599 = {
AD = "####";
AISLE = 6A;
DESCRIPTION = "Quaker Life Cereal";
R = 2;
REGULAR = "#.##";
};
40517 = {
AD = "###";
AISLE = 6A;
DESCRIPTION = "Toasted Oats";
R = 1;
REGULAR = "#.##";
};
};
};

Answer 1

Ok, I think your problem is the excessive creation of Array objects. So do the following instead of you're array creation:
NSDictionary *returnArray = [[NSJSONSerialization JSONObjectWithData:itemsData options:kNilOptions error:&error] valueForKey:#"items"];
for (NSDictionary *dict in returnArray in returnArray)
{
[self.objectsArray addObject:dict];
}
counter += 10;
[itemsTable reloadData];
What you'll get as you see is an array of NSDictionary objects, your return array is already an NSDictionary of dictionary objects. Also, slight observation, where are you resetting your counter?
EDIT: creating the NSDictionary from NSData:
[NSJSONSerialization JSONObjectWithData:self.requestData options:NSJSONReadingMutableContainers | NSJSONReadingMutableLeaves error:&error]
The requestData is generated using these delegate methods:
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
NSLog(#"In didReceiveResponse");
[self.requestData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
NSLog(#"In didReceiveData");
[self.requestData appendData:data];
}

Answer 2

I was able to find the issue in one line in the cellForRowAtIndexPath:. I commented out: cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; at the top and made sure it was only called once. I also did do a bit of cleanup as suggested by 8vius and now only once NSString is being allocated in that method call. Once I did these two things it was nice and responsive again without any stutters.