objective c - NSTableView Reload Data

Question

I'm developing an application, which works with tableview. I need to load VERY HUGE amount of data into my table view (up to 500k elements). When i load data, i show animation on another view. Animation runs in main thread. Loading data is on background thread. And i perform reload data in table view on background thread too. But i want to make it possible to cancel this operation.

And what i noticed is that fetching up my data lasts for several seconds while loading this data into table view can take up to minute. So, my question is: is there any way to interrupt loading data into table view? I've read tableview programming guide in documentation, but didn't found anything about such things there.

My target SDK is 10.6. I use cell-based tableview

Answer 1

I've got a solution, that suits me. So, what i did was adding a category to NSTableView with one property: lastRowVisible. I've overrode it's getter in such a way:

- (BOOL)isLastRowVisible
{
    NSRect bounds = self.superview.bounds;
    bounds.origin.y += bounds.size.height - 1;
    NSInteger index = [self rowAtPoint:bounds.origin];
    return index == ([self.dataSource numberOfRowsInTableView:self] - 1);
}

In my viewController i've added some properties:

@property (nonatomic, assign, readwrite) NSInteger pageNumber;
@property (nonatomic, assign, readwrite) NSInteger pageLimit;
@property (nonatomic, assign, readwrite) BOOL canLoadMoreData;

When I need loading data into tableView i do such a manipulation:

self.pageLimit = kDefaultPageLimit;
self.pageNumber = kDefaultPageNumber;

NSInteger visibleNumberOfRows = (self.pageNumber + 1) * self.pageLimit;
self.myDataArray = DataArray;
self.canLoadMoreData = (self.myDataArray.count < visibleNumberOfRows);

[self.myTableView reloadData];
[self.myTableView scrollRowToVisible:0];

And in my delegate methods i just check whether i need to load more data or not:

- (NSInteger)numberOfRowsInTableView:(NSTableView *)tableView
{
    return self.myData.count < self.visibleNumberOfRows ? self.myData.count : self.visibleNumberOfRows;
}

- (NSCell *)tableView:(NSTableView *)tableView dataCellForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
{   
    if (tableView.lastRowVisible && self.canLoadMoreData)
    {
        self.pageNumber ++;
        if (self.myData.count < self.visibleNumberOfRows)
        {
            self.canLoadMoreData = NO;
        }
        [tableView reloadData];
    }
    // configure and return cell
}

Such a solution works fine for me and suits all my needs.