Reloading data in tableView for invisible sections - ios

Question

Then I get json update I reload my tableView, but I have tableView with collectionView inside it and I have little lag in visible cell at the moment of reload. I want to reload only invisible cell of tableView. But there is no 'visibleSections' method like 'visibleCells'.
I get all visible sections
NSArray *visibleSections = [[self.tableView indexPathsForVisibleRows]valueForKey:#"section"];
Not I want get all sections, then remove all visibleSections and reload this new array. But I can not find the way to get all sections. How can I do it?

Answer 1

You could use one of these methods:
- (void)reloadRowsAtIndexPaths:withRowAnimation:
- (void)reloadSections:withRowAnimation:
Edit
When you try to get the indexPaths of all invisible cells, you could try something like this:
NSMutableArray *invisibleCells = [NSMutableArray array];
for (int i = 0; i < [tabsTableView numberOfSections]; i++) {
for (int n = 0; n < [tabsTableView numberOfRowsInSection:i]; n++) {
for (NSIndexPath *indexPath in [tabsTableView indexPathsForVisibleRows]) {
if ([indexPath section] == i && [indexPath row] == n) {
goto nextIteration;
}
}
[invisibleCells addObject:[NSIndexPath indexPathForRow:n inSection:i]];
nextIteration:;
}
}
More important is why you would like to do that?! Due UITableViewCells get reused, they won't be updatable. When the cell is "invisible", it changes its content and is used at a different position within the visible cells. This is how UITableView works.
You will (also currently) use this method to set the content of the cell:
- (void)tableView:tableView cellForRowAtIndexPath:indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:_cellID];
if (!cell) {
cell = (UITableViewCell *)[[[NSBundle mainBundle] loadNibNamed:#"cellTemplate" owner:nil options:nil] objectAtIndex:0];
}
// configure cell content here
}
When the cell get's reused, this method gets called and you create the cell only if UITableView does not reuse an invisible cell. If it does, you change the content.
So there is no need to reload invisible cells and it's impossible. From the docs:
Return Value
An object representing a cell of the table or nil if the cell is not visible or indexPath is out of range.