Views at depth with root view - recursive?

Question

I am trying to write a function to return all children of a view at a given depth :

/// Write the body of the function `views(atDepth:withRootView:)`
/// which should return all children of a view at a given depth.
/// Example of a view hierarchy:
///
/// 0:       view1
///            |
/// 1:       view2
///            |
/// 2:       view3
///         /     \
/// 3:   view4   view5
///        |       |
/// 4:   view6   view7
///                |
/// 5:           view8
///
/// Expected results for some calls with the hierarchy above:
/// `views(atDepth: 0, withRootView: view1) == [view1]`
/// `views(atDepth: 1, withRootView: view1) == [view2]`
/// `views(atDepth: 2, withRootView: view1) == [view3]`
/// `views(atDepth: 3, withRootView: view1) == [view4, view5]`
/// `views(atDepth: 4, withRootView: view1) == [view6, view7]` <-- The final boss test
/// `views(atDepth: 5, withRootView: view1) == [view8]`

This is what I wrote (and it's working) :

func views(atDepth depth: Int, withRootView rootView: UIView, currentRecursiveLevel:Int? = 0) -> [UIView] {
    var arr = [UIView]()
    if depth == 0 || currentRecursiveLevel == depth {
        arr.append(rootView)
    } else {
        for subview in rootView.subviews {
            arr.append(contentsOf: views(atDepth: depth, withRootView: subview, currentRecursiveLevel: currentRecursiveLevel! + 1))
        }
    }
    
    return arr
}

Can I (and how to ?) remove the parameter currentRecursiveLevel to have this definition :

func views(atDepth depth: Int, withRootView rootView: UIView) -> [UIView]

Answer 1

Solution provided by MrSmith42 :

func views(atDepth depth: Int, withRootView rootView: UIView) -> [UIView] {
    if depth == 0 {
        return [rootView]
    } else {
        var arr = [UIView]()
        for subview in rootView.subviews {
            arr.append(contentsOf: views(atDepth: depth - 1, withRootView: subview))
        }
        return arr
    }
}