how to properly use insertRowsAtIndexPaths?

Question

I went through all the examples online and could not figure out how to properly add a cell to a tableview with animation. Let's say I have one section with one cell and I want to add another cell once the user clicks on the first cell's accessory.

My "add" method does this:

- (IBAction) toggleEnabledTextForSwitch1onSomeLabel: (id) sender {  
if (switch1.on) {

    NSArray *appleComputers = [NSArray arrayWithObjects:@"WWWWW" ,@"XXXX", @"YYYY", @"ZZZZ", nil];
    NSDictionary *appleComputersDict = [NSDictionary dictionaryWithObject:appleComputers forKey:@"Computers"];
    [listOfItems replaceObjectAtIndex:0 withObject:appleComputersDict];
    [tblSimpleTable reloadData];

}

Which is working but there is no animation. I understand that in order to add animation, I need to use insertRowsAtIndexPaths:withRowAnimation, so I tried tons of options but it always crashes when executing the insertRowsAtIndexPaths:withRowAnimation method.

My recent try was by doing this:

- (IBAction) toggleEnabledTextForSwitch1onSomeLabel: (id) sender {  
if (switch1.on) {

    NSIndexPath *path1 = [NSIndexPath indexPathForRow:1 inSection:0]; //ALSO TRIED WITH indexPathRow:0
      NSArray *indexArray = [NSArray arrayWithObjects:path1,nil];   
     [tblSimpleTable insertRowsAtIndexPaths:indexArray withRowAnimation:UITableViewRowAnimationRight];

}
}  

What am I doing wrong? How can I make this happen easily? I dont understand this whole indexPathForRow thing...I also dont understand how with this method I can add a label name to the new cell. Please help...thanks!!

Answer 1

It's a two step process:

First update your data source so numberOfRowsInSection and cellForRowAtIndexPath will return the correct values for your post-insert data. You must do this before you insert or delete rows or you will see the "invalid number of rows" error that you're getting.

Then insert your row:

[tblSimpleTable beginUpdates];
[tblSimpleTable insertRowsAtIndexPaths:indexArray withRowAnimation:UITableViewRowAnimationRight];
[tblSimpleTable endUpdates];

Simply inserting or deleting a row doesn't change your data source; you have to do that yourself.

Answer 2

The important thing to keep in mind when using insertRowsAtIndexPaths is that your UITableViewDataSource needs to match what the insert is telling it to do. If you add a row to the tableview, make sure the backing data is already updated to match.

Answer 3

First of all, you should update your data model just before update table itself. Also you can use:

[tableView beginUpdates];
// do all row insertion/delete here
[tableView endUpdates];

And table will produce all changed at once with animation (if you specify it)