Swift find superview of given class with generics - swift

Question

I guess I'm struggling with generics. I want to create simple UIView extension to find recursively a superview of class passed in the function param. I want the function to return optional containing obviously either nil, or object visible as instance of provided class.
extension UIView {
func superviewOfClass<T>(ofClass: T.Type) -> T? {
var currentView: UIView? = self
while currentView != nil {
if currentView is T {
break
} else {
currentView = currentView?.superview
}
}
return currentView as? T
}
}
Any help much appreciated.

Answer 1

Swift 3/4
This is a more concise way:
extension UIView {
func superview<T>(of type: T.Type) -> T? {
return superview as? T ?? superview.compactMap { $0.superview(of: type) }
}
func subview<T>(of type: T.Type) -> T? {
return subviews.compactMap { $0 as? T ?? $0.subview(of: type) }.first
}
}
Usage:
let tableView = someView.superview(of: UITableView.self)
let tableView = someView.subview(of: UITableView.self)

Answer 2

No need to pass in the type of the class you want (at least in Swift 4.1)…
extension UIView {
func firstSubview<T: UIView>() -> T? {
return subviews.compactMap { $0 as? T ?? $0.firstSubview() as? T }.first
}
}

Answer 3

I'm using this.
// Lookup view ancestry for any `UIScrollView`.
if let scrollView = view.searchViewAnchestors(for: UIScrollView.self) {
print("Found scrollView: \(scrollView)")
}
Extension is really a single statement.
extension UIView {
func searchViewAnchestors<ViewType: UIView>(for viewType: ViewType.Type) -> ViewType? {
if let matchingView = self.superview as? ViewType {
return matchingView
} else {
return superview?.searchViewAnchestors(for: viewType)
}
}
}
With this alternative implementation below, you can actually let the call site determine what type to look for, but I found it somewhat unconventional.
extension UIView {
func searchInViewAnchestors<ViewType: UIView>() -> ViewType? {
if let matchingView = self.superview as? ViewType {
return matchingView
} else {
return superview?.searchInViewAnchestors()
}
}
}
You can call it like this.
if let scrollView: UIScrollView = view.searchInViewAnchestors() {
print("Found scrollView: \(scrollView)")
}