How to animate UITableViewCell height using auto-layout?

Question

There are lot of similar questions on Stack Overflow about UITableViewCell height animation, but nothing works for new iOS8 auto-layout driven table view. My is

Answer 1

I would like to add a few points to Alex's answer.

If you call beginUpdates and endUpdates inside cellForRowAtIndexPath or willDisplayCell, your app will crash. After animating your cell's increase, you might want it stay the same after scrolling to your tableView. You might also want that the rest of the cells keep their height the same. But remember that cells are reusable, so you might end up with other cells having increased height.

As a result, you will have to set the constraint constant inside cellForRowAtIndexPath depending on the item it represents. But if you call layoutIfNeeded afterwards, it will display a warning with your constraints. My belief is that it attempts to generate the cell layout before its new height is computed.

public func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
...
    myConstraint.constant = itemForCell.value == "x" ? 50 : 20 // stop right here
    cell.layoutIfNeeded() <- don't do this or some of your constraints will break
    beginUpdates() <-- if you do this your app will crash
    endUpdates() <-- same here