Have a reloadData for a UITableView animate when changing

I have a UITableView that has two modes. When we switch between the modes I have a different number of sections and cells per section. Ideally, it would do some cool animation when the table grows or shrinks.

Here is the code I tried, but it doesn't do anything:

CGContextRef context = UIGraphicsGetCurrentContext(); 
[UIView beginAnimations:nil context:context]; 
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; 
[UIView setAnimationDuration:0.5]; 

[self.tableView reloadData];
[UIView commitAnimations];

Any thoughts on how I could do this?

Actually, it's very simple:

[_tableView reloadSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:UITableViewRowAnimationFade];

From the documentation:

Calling this method causes the table view to ask its data source for new cells for the specified sections. The table view animates the insertion of new cells in as it animates the old cells out.

You might want to use:

Objective-C

[UIView transitionWithView: self.tableView
                  duration: 0.35f
                   options: UIViewAnimationOptionTransitionCrossDissolve
                animations: ^(void)
 {
      [self.tableView reloadData];
 }
                completion: nil];

Swift

UIView.transitionWithView(tableView,
                          duration: 0.35,
                          options: .TransitionCrossDissolve,
                          animations:
{ () -> Void in
    self.tableView.reloadData()
},
                          completion: nil);

Swift 3, 4 & 5

UIView.transition(with: tableView,
                  duration: 0.35,
                  options: .transitionCrossDissolve,
                  animations: { self.tableView.reloadData() }) // left out the unnecessary syntax in the completion block and the optional completion parameter

No hassles. :D

You can also use any of the UIViewAnimationOptionTransitions you want for cooler effects:

• transitionNone
• transitionFlipFromLeft
• transitionFlipFromRight
• transitionCurlUp
• transitionCurlDown
• transitionCrossDissolve
• transitionFlipFromTop
• transitionFlipFromBottom

Have more freedom using CATransition class.

It isn't limited to fading, but can do movements as well..

For example:

(don't forget to import QuartzCore)

CATransition *transition = [CATransition animation];
transition.type = kCATransitionPush;
transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
transition.fillMode = kCAFillModeForwards;
transition.duration = 0.5;
transition.subtype = kCATransitionFromBottom;

[[self.tableView layer] addAnimation:transition forKey:@"UITableViewReloadDataAnimationKey"];

Change the type to match your needs, like kCATransitionFade etc.

Implementation in Swift:

let transition = CATransition()
transition.type = kCATransitionPush
transition.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
transition.fillMode = kCAFillModeForwards
transition.duration = 0.5
transition.subtype = kCATransitionFromTop
self.tableView.layer.addAnimation(transition, forKey: "UITableViewReloadDataAnimationKey")
// Update your data source here
self.tableView.reloadData()

Reference for CATransition

Swift 5:

let transition = CATransition()
transition.type = CATransitionType.push
transition.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut)
transition.fillMode = CAMediaTimingFillMode.forwards
transition.duration = 0.5
transition.subtype = CATransitionSubtype.fromTop
self.tableView.layer.add(transition, forKey: "UITableViewReloadDataAnimationKey")
// Update your data source here
self.tableView.reloadData()

I believe you can just update your data structure, then:

[tableView beginUpdates];
[tableView deleteSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:YES];
[tableView insertSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:YES];
[tableView endUpdates];

Also, the "withRowAnimation" is not exactly a boolean, but an animation style:

UITableViewRowAnimationFade,
UITableViewRowAnimationRight,
UITableViewRowAnimationLeft,
UITableViewRowAnimationTop,
UITableViewRowAnimationBottom,
UITableViewRowAnimationNone,
UITableViewRowAnimationMiddle

All of these answers assume that you are using a UITableView with only 1 section.

To accurately handle situations where you have more than 1 section use:

NSRange range = NSMakeRange(0, myTableView.numberOfSections);
NSIndexSet *indexSet = [NSIndexSet indexSetWithIndexesInRange:range];
[myTableView reloadSections:indexSet withRowAnimation:UITableViewRowAnimationAutomatic];

(Note: you should make sure that you have more than 0 sections!)

Another thing to note is that you may run into a NSInternalInconsistencyException if you attempt to simultaneously update your data source with this code. If this is the case, you can use logic similar to this:

int sectionNumber = 0; //Note that your section may be different

int nextIndex = [currentItems count]; //starting index of newly added items

[myTableView beginUpdates];

for (NSObject *item in itemsToAdd) {
    //Add the item to the data source
    [currentItems addObject:item];

    //Add the item to the table view
    NSIndexPath *path = [NSIndexPath indexPathForRow:nextIndex++ inSection:sectionNumber];
    [myTableView insertRowsAtIndexPaths:[NSArray arrayWithObject:path] withRowAnimation:UITableViewRowAnimationAutomatic];
}

[myTableView endUpdates];