Question

i use a table view with custom values and image.

Every rows do this:
– Check device (iphone/ipad)
– Parse a wordpress xml
– Split this string “Thu, 13 Jan 2011 22:26:27 +0000” and get pos[1] and pos[2].
– Convert “Jan” in “Gennaio”
– set values in row cell

It’s make in this way:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {    
    @try {
        newsRow = ((NewsRowController *)[tableView dequeueReusableCellWithIdentifier:@"cell"]);
        if (newsRow == nil) {

            if ( [[Device GetModel] isEqualToString:@"iPad Simulator"] || [[Device GetModel] isEqualToString:@"iPad"])
                [[NSBundle mainBundle] loadNibNamed:@"NewsRow_ipad" owner:self options:nil];
            else [[NSBundle mainBundle] loadNibNamed:@"NewsRow" owner:self options:nil];

            if ([tableArray count] > 0) {               
                NSArray *chunks = [[dataArray objectAtIndex:indexPath.row] componentsSeparatedByString: @" "];

                [newsRow setCellDataWithName:[tableArray objectAtIndex:indexPath.row]  
                                     andDate:[descArray objectAtIndex:indexPath.row] 
                                         day:[chunks objectAtIndex:1] 
                                       month:[self convertMonthToExtended:[chunks objectAtIndex:2]]];
            }
        }       
    }
    @catch (NSException * e) {
        NSLog(@"OK, crashato. Sappiamo il perchè!");
    }

    return newsRow;
}

the function convertMonthToExtended do this:

if ([small isEqualToString:@"Jan"]) return @"gennaio";
[...]
if ([small isEqualToString:@"Dec"]) return @"dicembre";

Now, on simulator it works very fine, but on device, a 3G device in particular, when i scroll the table it scroll slowly because i do a lot of things.

How can i speed up the scroll?
What is correct way to re-implement this function to be more fast?
How can i optimize this snippet?

Any idea please?

thanks,
A

Answer 1

I think that you can move the following code:

if ( [[Device GetModel] isEqualToString:@"iPad Simulator"] || [[Device GetModel] isEqualToString:@"iPad"])
                [[NSBundle mainBundle] loadNibNamed:@"NewsRow_ipad" owner:self options:nil];
            else [[NSBundle mainBundle] loadNibNamed:@"NewsRow" owner:self options:nil];

Outside the tableView:cellForRowAtIndexPath: method because you don’t need to do this check for every row (the device doesn’t change from line to line). And you can put this code in viewDidLoad .

I suggest you do all the computations and the work of asynchronous network.
You can precomputare all the information you need to populate the rows and save them in such a NSArray while viewing a UIProgressView or something like that, only after all the operations populate the table view.
You can use the [Tableview reloadData] method to reload all data in the table view, this mean that numberOfSectionsInTableView: , tableView:numberOfRowsInSection:, and all the data source method are recalled.