how to properly use insertRowsAtIndexPaths? - iphone

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)

Answer 4

The insertRowsAtIndexPaths:withRowAnimation: AND the changes to your data model both need to occur in-between beginUpdates and endUpates
I've created a simple example that should work on its own. I spent a week fiddling around trying to figure this out since I couldn't find any simple examples, so I hope this saves someone time and headache!
#interface MyTableViewController ()
#property (nonatomic, strong) NSMutableArray *expandableArray;
#property (nonatomic, strong) NSMutableArray *indexPaths;
#property (nonatomic, strong) UITableView *myTableView;
#end
#implementation MyTableViewController
- (void)viewDidLoad
{
[self setupArray];
}
- (void)setupArray
{
self.expandableArray = #[#"One", #"Two", #"Three", #"Four", #"Five"].mutableCopy;
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return self.expandableArray.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
//here you should create a cell that displays information from self.expandableArray, and return it
}
//call this method if your button/cell/whatever is tapped
- (void)didTapTriggerToChangeTableView
{
if (/*some condition occurs that makes you want to expand the tableView*/) {
[self expandArray]
}else if (/*some other condition occurs that makes you want to retract the tableView*/){
[self retractArray]
}
}
//this example adds 1 item
- (void)expandArray
{
//create an array of indexPaths
self.indexPaths = [[NSMutableArray alloc] init];
for (int i = theFirstIndexWhereYouWantToInsertYourAdditionalCells; i < theTotalNumberOfAdditionalCellsToInsert + theFirstIndexWhereYouWantToInsertYourAdditionalCells; i++) {
[self.indexPaths addObject:[NSIndexPath indexPathForRow:i inSection:0]];
}
//modify your array AND call insertRowsAtIndexPaths:withRowAnimation: INBETWEEN beginUpdates and endUpdates
[self.myTableView beginUpdates];
//HERE IS WHERE YOU NEED TO ALTER self.expandableArray to have the additional/new data values, eg:
[self.expandableArray addObject:#"Six"];
[self.myTableView insertRowsAtIndexPaths:self.indexPaths withRowAnimation:(UITableViewRowAnimationFade)]; //or a rowAnimation of your choice
[self.myTableView endUpdates];
}
//this example removes all but the first 3 items
- (void)retractArray
{
NSRange range;
range.location = 3;
range.length = self.expandableArray.count - 3;
//modify your array AND call insertRowsAtIndexPaths:withRowAnimation: INBETWEEN beginUpdates and endUpdates
[self.myTableView beginUpdates];
[self.expandableArray removeObjectsInRange:range];
[self.myTableView deleteRowsAtIndexPaths:self.indexPaths withRowAnimation:UITableViewRowAnimationFade]; //or a rowAnimation of your choice
[self.myTableView endUpdates];
}
#end

Answer 5

For the swift users
// have inserted new item into data source
// update
self.tableView.beginUpdates()
var ip = NSIndexPath(forRow:find(self.yourDataSource, theNewObject)!, inSection: 0)
self.tableView.insertRowsAtIndexPaths([ip], withRowAnimation: UITableViewRowAnimation.Fade)
self.tableView.endUpdates()