Description that can be used with any type that has recursive children

HierarchyDescription.swift

public protocol HierarchyDescription {
    associatedtype Child: HierarchyDescription
    var children: [Child] { get }
    var description: String { get }
}

extension HierarchyDescription {
    public var hierarchyDescription: String {
        var description = self.description
        for child in children {
            description += "\n  " + child.hierarchyDescription
                .replacingOccurrences(of: "\n", with: "\n  ")
        }
        return description
    }
}

extension HierarchyDescription where Self == Child {
    public func hierarchyDescription(customDescription: (Self) -> String = \.description) -> String {
        var description = customDescription(self)
        for child in children {
            description += "\n  " + child.hierarchyDescription(customDescription: customDescription)
                .replacingOccurrences(of: "\n", with: "\n  ")
        }
        return description
    }
    
    public var allChildren: [Child] {
        children + children.flatMap { $0.allChildren }
    }
}

UIView+HierarchyDescription.swift

extension UIView: HierarchyDescription {
    public var children: [UIView] { subviews }
}

zExample.swift

let datePicker = UIDatePicker()
print(datePicker.hierarchyDescription)
//<UIDatePicker: 0x7f9f35f580c0; frame = (0 0; 221.667 34.3333); layer = <CALayer: 0x600000862c40>>
//  <_UIDatePickerIOSCompactView: 0x7f9f35f58280; frame = (0 0; 0 0); gestureRecognizers = <NSArray: 0x60000028d410>; layer = <CALayer: 0x600000862800>>
//    <UIView: 0x7f9f35f57f30; frame = (0 0; 0 0); layer = <CALayer: 0x6000008625e0>>
//      <UIView: 0x7f9f35f584a0; frame = (0 0; 0 0); layer = <CALayer: 0x600000862840>>
//      <_UIDatePickerLinkedLabel: 0x7f9f35f58610; frame = (0 0; 0 0); layer = <CALayer: 0x600000862880>>
//        <UILabel: 0x7f9f35f589d0; frame = (0 0; 0 0); text = '11/30/20'; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x600002ef63f0>>
//    <UIView: 0x7f9f35f592d0; frame = (0 0; 0 0); layer = <CALayer: 0x6000008628a0>>
//      <UIView: 0x7f9f35f59440; frame = (0 0; 0 0); layer = <CALayer: 0x600000862940>>
//      <UILabel: 0x7f9f35f595b0; frame = (0 0; 0 0); text = '12:11 PM'; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x600002ef6760>>

print((datePicker as UIView).allChildren.last)
//<UILabel: 0x7f9f35f595b0; frame = (0 0; 0 0); text = '12:11 PM'; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x600002ef6760>>