UITableView top to topLayoutGuide programmatically content inset - uitableview

Question

Due to my attempt to implement iAds "properly" (i.e., sharing a single instance of ADBannerView), I am creating a UITableView programatically inside a UIViewController and adding it to the view. Below are a couple of snippets from my subclass of UIViewController:
From viewDidLoad
self.tableView = UITableView(frame: self.view.bounds, style: .Grouped)
self.tableView.allowsSelectionDuringEditing = true
self.tableView.registerNib(UINib(nibName: "TableViewCellWithSwitch", bundle: nil), forCellReuseIdentifier: "SliderCellIdentifier")
self.tableView.dataSource = self
self.tableView.setTranslatesAutoresizingMaskIntoConstraints(false)
self.view.addSubview(self.tableView)
self.tableViewBottomLayoutConstraint = NSLayoutConstraint(item: self.tableView, attribute: .Bottom, relatedBy: .Equal, toItem: self.bottomLayoutGuide, attribute: .Top, multiplier: 1, constant: 0)
self.view.addConstraints([
NSLayoutConstraint(item: self.tableView, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1, constant: 0),
//NSLayoutConstraint(item: self.tableView, attribute: .Top, relatedBy: .Equal, toItem: self.view, attribute: .Top, multiplier: 1, constant: 0),
//NSLayoutConstraint(item: self.tableView, attribute: .Top, relatedBy: .Equal, toItem: self.view, attribute: .Top, multiplier: 1, constant: self.topLayoutGuide.length),
//NSLayoutConstraint(item: self.tableView, attribute: .Top, relatedBy: .Equal, toItem: self.topLayoutGuide, attribute: .Bottom, multiplier: 1, constant: 0),
NSLayoutConstraint(item: self.tableView, attribute: .Right, relatedBy: .Equal, toItem: self.view, attribute: .Right, multiplier: 1, constant: 0),
self.tableViewBottomLayoutConstraint
])
// This must be called or the use of self.topLayoutGuide will not function
// See: https://developer.apple.com/library/ios/documentation/uikit/reference/UIViewController_Class/index.html#//apple_ref/occ/instp/UIViewController/topLayoutGuide
self.view.layoutSubviews()
iAds implementation (added to try and justify, rightly or wrongly, my implementation of the UITableView)
func showiAds(animated: Bool) {
println("Show iAd")
if !self.showingiAd {
println("Showing iAd")
self.showingiAd = true
// Add the banner view below the content before it's then animated in to view
let delegate = UIApplication.sharedApplication().delegate as AppDelegate
let bannerView = delegate.bannerView
self.bannerBottomConstraint = NSLayoutConstraint(item: bannerView, attribute: .Bottom, relatedBy: .Equal, toItem: self.bottomLayoutGuide, attribute: .Top, multiplier: 1, constant: bannerView.frame.size.height)
if (bannerView.superview != self.view) {
bannerView.removeFromSuperview()
}
self.view.addSubview(bannerView)
self.view.addConstraints([
self.bannerBottomConstraint,
NSLayoutConstraint(item: bannerView, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1, constant: 0),
NSLayoutConstraint(item: bannerView, attribute: .Right, relatedBy: .Equal, toItem: self.view, attribute: .Right, multiplier: 1, constant: 0),
])
self.view.layoutIfNeeded()
// Only the changing of the value of the top of the banner is animated so it "slides in" from the bottom
self.bannerBottomConstraint.constant = 0
self.view.setNeedsUpdateConstraints()
UIView.animateWithDuration(animated ? 0.5 : 0, animations: { () -> Void in
// Calling layoutIfNeeded here will animate the layout constraint cosntant change made above
self.view.layoutIfNeeded()
}, completion: { (completed) -> Void in
if completed {
println("Completed animation")
}
})
}
}
func hideiAds() {
println("Hide iAd")
if self.self.showingiAd {
self.showingiAd = false
println("Hiding iAd")
let delegate = UIApplication.sharedApplication().delegate as AppDelegate
let bannerView = delegate.bannerView
if bannerView.superview == self.view {
bannerView.removeFromSuperview()
}
self.view.removeConstraint(self.tableViewBottomLayoutConstraint)
self.tableViewBottomLayoutConstraint = NSLayoutConstraint(item: self.tableView, attribute: .Bottom, relatedBy: .Equal, toItem: self.bottomLayoutGuide, attribute: .Top, multiplier: 1, constant: 0)
self.view.addConstraint(self.tableViewBottomLayoutConstraint)
}
}
As you can see, there are 3 constraints commented out. Each of these seem to have different results. I won't post screenshots of them (unless requested), but I will describe them.
NSLayoutConstraint(item: self.tableView, attribute: .Top, relatedBy: .Equal, toItem: self.view, attribute: .Top, multiplier: 1, constant: 0)
iOS 7: Top of table and content of table is at the top of screen. Content is behind the navigation bar
iOS 8: Top of table and content of table is below the navigation bar. Content is below the navigation bar (correct)
NSLayoutConstraint(item: self.tableView, attribute: .Top, relatedBy: .Equal, toItem: self.view, attribute: .Top, multiplier: 1, constant: self.topLayoutGuide.length)
iOS 7: Top of table and content of table is at the top of screen. Content is behind the navigation bar
iOS 8: Top of table and content of table is below the navigation bar. Content is below the navigation bar (correct)
NSLayoutConstraint(item: self.tableView, attribute: .Top, relatedBy: .Equal, toItem: self.topLayoutGuide, attribute: .Bottom, multiplier: 1, constant: 0)
iOS 7: Top of table and content of table is below the navigation bar. Content is below the navigation bar (correct)
iOS 8: Top of table is at the bottom of the navigation bar (correct), but content of table is below the navigation bar, plus (what looks like) the height of the offset again (incorrect)
I am aware that I could just do an if iOS7 {...} else {...}, but that feels pretty dirty and I've got a feeling it's my lack of understanding that's causing this issue, so I'd like to figure out how to have this work on iOS 7 and 8 without having resort to version checking, if possible.

Answer 1

I ended up finding a way of doing this. I'm not sure just how hacky it is, but it's worked on iOS 7.0-8.2 so far.
override func viewDidLayoutSubviews() {
if self.tableView != nil {
// Setting both of these to 0 seems to fix some auto layout issues that crop up in iOS 7/8 depending on
// which item the layout is to, e.g., in iOS 8, having the UITableView's top be to the topLayoutGuide's bottom will
// cause a gap at the top of the UITableView, but this removes that gap and doesn't seem to affect iOS 7
self.tableView.contentInset = UIEdgeInsetsZero
self.tableView.scrollIndicatorInsets = UIEdgeInsetsZero
if self.showingiAd {
let delegate = UIApplication.sharedApplication().delegate as AppDelegate
if let bannerView = delegate.bannerView {
let bannerViewHeight = bannerView.frame.size.height
self.tableViewBottomLayoutConstraint.constant = -bannerViewHeight
}
}
}
}