How to animate UITableView header view

Question

I need to animate the insertion of a tableview header view. I want that the table rows to slide down while the header view expands its frame.
So far the best result I go

Answer 1

Here's what I got to work in Swift, with an initial frame height of zero and updating it to its full height in the animations closure:

// Calculate new frame size for the table header
var newFrame = tableView.tableHeaderView!.frame
newFrame.size.height = 42

// Get the reference to the header view
let tableHeaderView = tableView.tableHeaderView

// Animate the height change
UIView.animate(withDuration: 0.6) {
    tableHeaderView.frame = newFrame
    self.tableView.tableHeaderView = tableHeaderView
})