How to expand section in tableview in iOS? - ios

Question

I have a custom header for each section in tableView, and the headerView has a button. On click of that button, I'm trying to expand the section by changing the number of rows for that section. It works fine if I call reloadData, but it crashes when I try to use reloadSections/ insert/delete sections.
HEre is my number of rows method:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
if (highlighHeaderClicked) {
return [_expandCountArray[section]integerValue]; // 9,9,9
}
return [_collapseCountArray[section]integerValue]; //2,2,2
}
So by default tableView shows 2 rows, when button is clicked, I want to show 9 rows.
and the button action method:
-(IBAction)highlightHeaderClicked:(id)sender{
highlighHeaderClicked = !highlighHeaderClicked;
NSIndexPath *indexPath = [self getIndexPathForView:sender];
NSIndexSet *indexSet = [NSIndexSet indexSetWithIndex:indexPath.length-1];
[self.tableView beginUpdates];
[self.tableView deleteSections:indexSet withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView insertSections:indexSet withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView endUpdates];
}
By doing this I got the excpetion:
Invalid update: invalid number of rows in section 2. The number of rows contained in an existing section after the update (9) must be equal to the number of rows contained in that section before the update (2), plus or minus the number of rows inserted or deleted from that section (0 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).
I also tried removing the object from datasource when the button action method gets called.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [_tempRowCountArray[section]integerValue]; //2,2,2
}
-(IBAction)highlightHeaderClicked:(id)sender{
highlighHeaderClicked = !highlighHeaderClicked;
NSIndexPath *indexPath = [self getIndexPathForView:sender];
NSIndexSet *indexSet = [NSIndexSet indexSetWithIndex:indexPath.length-1];
NSInteger rowCount = _mainDataSet.dashboardArray.count;
if (rowCount > 2) {
if (highlighHeaderClicked) {
[_tempRowCountArray replaceObjectAtIndex:indexPath.length withObject:#(rowCount)];
}else{
[_tempRowCountArray replaceObjectAtIndex:indexPath.length withObject:#2];
}
[self.tableView beginUpdates];
[self.tableView deleteSections:indexSet withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView insertSections:indexSet withRowAnimation:UITableViewRowAnimationBottom];
[self.tableView endUpdates];
}
}
What am I missing here ? I think I am passing the right array count each time.

Answer 1

The basic problem you have is that you are trying to insert and remove whole sections. That means the number of sections would have to change.
Instead, you have to remove and insert rows in sections.
Also, you have to specify the exact difference between the previous state and the new state.
For example:
NSArray *rowsToBeAdded = ...
NSArray *rowsToBeRemoved = ...
[self.tableView beginUpdates];
[self.tableView insertRowsAtIndexPaths:rowsToBeAdded withRowAnimation: UITableViewRowAnimationBottom];
[self.tableView deleteRowsAtIndexPaths:rowsToBeRemoved withRowAnimation: UITableViewRowAnimationBottom];
[self.table endUpdates];
That also means you have to be very careful about your logic and keep track of the sections that are expanded.
You have to return the correct number of items for collapses and expanded sections:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
BOOL expanded = ...;
if (!expanded) {
return 0;
}
return ...
}
One other solution for this problem is to keep the rows always there and avoid inserts & deletes completely. You can return zero height for all hidden rows.
To update the height of all rows, you then simply call:
[self.tableView beginUpdates];
[self.tableView endUpdates];