UIView+Find.swift

 
extension Collection where Element: UIView {
    /// Returns an array containing, in order, the views of the sequence that satisfy the given predicate.
    ///
    /// - Parameters:
    ///   - recursive: Boolean that indicates if filtering recursively
    ///   - isIncluded: A closure that takes a view of the sequence as its argument and returns a Boolean value indicating whether the view should be included in the returned array.
    /// - Returns: An array of the views that isIncluded allowed.
    func filter(recursive: Bool = false, _ isIncluded: (UIView) -> Bool) -> [UIView] {
        return reduce(into: []) { partialResult, view in
            if isIncluded(view) {
                partialResult.append(view)
            }
            if recursive, !view.subviews.isEmpty {
                let filteredSubviews = view.findSubviews(recursive: recursive, isIncluded)
                partialResult.append(contentsOf: filteredSubviews)
            }
        }
    }
}

extension UIView {
    /// Returns an array containing, in order, the subviews that satisfy the given predicate.
    ///
    /// - Parameters:
    ///   - recursive: Boolean that indicates if filtering the subviews
    ///   - isIncluded: A closure that takes a subview as its argument and returns a Boolean value indicating whether the view should be included in the returned array.
    /// - Returns: An array of the views that isIncluded allowed.
    func findSubviews(recursive: Bool = false, _ isIncluded: (UIView) -> Bool) -> [UIView] {
        return subviews.filter(recursive: recursive, isIncluded)
    }
}
 

You can simplify it further:

extension UIView {
  func subviews(recursively: Bool = false) -> [UIView] {
    guard recursively else { return subviews }
    return subviews.flatMap { [$0] + $0.subviews(recursively: true) }
  }
  
  func subviews(recursively: Bool = false, satisfy: (UIView) -> Bool) -> [UIView] {
    return subviews(recursively: recursively).filter(satisfy)
  }
}