Objective-c: how to properly add more rows to a UITableView - ios

Question

I know that there are a lot of similar questions to this one, but i didn't find any well-explained one yet.
I have a UITableView that gets its content (which is JSON) from a url, i'm using this method for fetching the JSON data:
-(void)getContents
{
NSString *contentStartString = [NSString stringWithFormat:#"%ld",(long)contentStart];
NSString *contentCountString = [NSString stringWithFormat:#"%ld",(long)contentCount];
NSString *contentsUrl = #"http://www.ana.fm/api/index.php?start=";
contentsUrl = [contentsUrl stringByAppendingString:contentStartString];
contentsUrl = [contentsUrl stringByAppendingString:#"&count="];
contentsUrl = [contentsUrl stringByAppendingString:contentCountString];
NSLog(#"%#",contentsUrl);
NSURL *URL = [NSURL URLWithString:contentsUrl];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
//AFNetworking asynchronous url request
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]
initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"%#", responseObject);
jsonContents = [responseObject objectForKey:#"contents"];
[self.tableView reloadData];
tableLoadMoreCapability = true;
} failure:nil];
[operation start];
}
This works perfectly, but then when i reach the end of the table which i can detect using this method:
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
float endScrolling = scrollView.contentOffset.y + scrollView.frame.size.height;
if (endScrolling >= scrollView.contentSize.height)
{
if(tableLoadMoreCapability == true){
contentStart = contentStart + 20;
[self updateContentsTable];
}
}
}
As you see i want to execute this method updateContentsTable (when reaching the end of the table) which is this one:
- (void)updateContentsTable
{
tableLoadMoreCapability = false;
NSLog(#"load more rows");
NSString *contentStartString = [NSString stringWithFormat:#"%ld",(long)contentStart];
NSString *contentCountString = [NSString stringWithFormat:#"%ld",(long)contentCount];
NSString *contentsUrl = #"http://www.ana.fm/api/index.php?start=";
contentsUrl = [contentsUrl stringByAppendingString:contentStartString];
contentsUrl = [contentsUrl stringByAppendingString:#"&count="];
contentsUrl = [contentsUrl stringByAppendingString:contentCountString];
NSLog(#"%#",contentsUrl);
NSURL *URL = [NSURL URLWithString:contentsUrl];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
//AFNetworking asynchronous url request
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]
initWithRequest:request];
operation.responseSerializer = [AFJSONResponseSerializer serializer];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"%#", responseObject);
jsonContents = [responseObject objectForKey:#"contents"];
[self.tableView reloadData];
} failure:nil];
[operation start];
}
Now i'm using [self.tableView reloadData]; so the code works and the table reloaded with the new data, i don't want that, i need the new rows to be inserted below the old ones, i learned from other answers that i have to use [self.tableView insertRowsAtIndexPaths: .....] but i didn't understand how to do that.
Anyone can clarify how to do that ?
Thanks in advance.

Answer 1

I think you are doing more work than you need. Why not tell the table view that the number of rows you have is larger than the number you get with your first call? Then, as soon as the delegate is asked for a cell at a row beyond the ones you have actually loaded (indicating that the user has scrolled past the data you have available), you then get your next batch of data via JSON. Through the delegate methods, you have precise control over what data is shown in the visible cells. I would avoid the scrolling stuff completely.
The only care you need to take is when (and how) you reload the table: you want to avoid reload calling reload calling reload....
Think of the rows of the table as a window sliding over a (virtual) table of all your rows.