Get notified when UITableView has finished asking for data?

This answer doesn't seem to be working anymore, due to some changes made to UITableView implementation since the answer was written. See this comment : Get notified when UITableView has finished asking for data?

I've been playing with this problem for a couple of days and think that subclassing UITableView's reloadData is the best approach :

- (void)reloadData {

    NSLog(@"BEGIN reloadData");

    [super reloadData];

    NSLog(@"END reloadData");

}

reloadData doesn't end before the table has finish reload its data. So, when the second NSLog is fired, the table view has actually finish asking for data.

I've subclassed UITableView to send methods to the delegate before and after reloadData. It works like a charm.

I did have a same scenario in my app and thought would post my answer to you guys as other answers mentioned here does not work for me for iOS7 and later

Finally this is the only thing that worked out for me.

[yourTableview reloadData];

dispatch_async(dispatch_get_main_queue(),^{
        NSIndexPath *path = [NSIndexPath indexPathForRow:yourRow inSection:yourSection];
        //Basically maintain your logic to get the indexpath
        [yourTableview scrollToRowAtIndexPath:path atScrollPosition:UITableViewScrollPositionTop animated:YES];
 });

Swift Update:

yourTableview.reloadData()
dispatch_async(dispatch_get_main_queue(), { () -> Void in
    let path : NSIndexPath = NSIndexPath(forRow: myRowValue, inSection: mySectionValue)
    //Basically maintain your logic to get the indexpath
    yourTableview.scrollToRowAtIndexPath(path, atScrollPosition: UITableViewScrollPosition.Top, animated: true)

})

So how this works.

Basically when you do a reload the main thread becomes busy so at that time when we do a dispatch async thread, the block will wait till the main thread gets finished. So once the tableview has been loaded completely the main thread will gets finish and so it will dispatch our method block

Tested in iOS7 and iOS8 and it works awesome;)

Update for iOS9: This just works fine is iOS9 also. I have created a sample project in github as a POC. https://github.com/ipraba/TableReloadingNotifier

I am attaching the screenshot of my test here.

Tested Environment: iOS9 iPhone6 simulator from Xcode7

EDIT: This answer is actually not a solution. It probably appears to work at first because reloading can happen pretty fast, but in fact the completion block doesn't necessarily get called after the data has fully finished reloading - because reloadData doesn't block. You should probably search for a better solution.

To expand on @Eric MORAND's answer, lets put a completion block in. Who doesn't love a block?

@interface DUTableView : UITableView

   - (void) reloadDataWithCompletion:( void (^) (void) )completionBlock;

@end

and...

#import "DUTableView.h"

@implementation DUTableView

- (void) reloadDataWithCompletion:( void (^) (void) )completionBlock {
    [super reloadData];
    if(completionBlock) {
        completionBlock();
    }
}

@end

Usage:

[self.tableView reloadDataWithCompletion:^{
                                            //do your stuff here
                                        }];

reloadData just asking for data for the visible cells. Says, to be notified when specify portion of your table is loaded, please hook the tableView: willDisplayCell: method.

- (void) reloadDisplayData
{
    isLoading =  YES;
    NSLog(@"Reload display with last index %d", lastIndex);
    [_tableView reloadData];
    if(lastIndex <= 0){
    isLoading = YES;
    //Notify completed
}

- (void) tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if(indexPath.row >= lastIndex){
    isLoading = NO;
    //Notify completed
}