Swift: Recursively cycle through all subviews to find a specific class and append to an array

Question

Having a devil of a time trying to figure this out. I asked a similar question here: Swift: Get all subviews of a specific type and add to an array

While this works, I realized there are many subviews and sub-sub views, and so I need a function that starts at the main UIView, cycles through all the subviews (and their subviews until there aren't any left) and adds it to an array for a custom button class which I have named CheckCircle.

Essentially I'd like to end up with an array of CheckCircles which constitute all the CheckCircles added to that view programmatically.

Any ideas? Here's what I've been working on. It doesn't seem to be appending any Checkcircles to the array:

    func getSubviewsOfView(v:UIView) -> [CheckCircle] {
        var circleArray = [CheckCircle]()
        // Get the subviews of the view

        var subviews = v.subviews

        if subviews.count == 0 {
            return circleArray
        }

        for subview : AnyObject in subviews{
  if let viewToAppend = subview as? CheckCircle {
        circleArray.append(viewToAppend as CheckCircle)
      }
            getSubviewsOfView(subview as! UIView)
        }
        return circleArray
    }

Solution 1

Your main problem is that when you call getSubviewsOfView(subview as! UIView) (recursively, within the function), you aren't doing anything with the result.

You also can delete the count == 0 check, since in that case the for…in loop will just be skipped. You also have a bunch of unnecessary casts

Assuming your desire is to get a flat array of CheckCircle instances, I think this adaptation of your code should work:

func getSubviewsOfView(v:UIView) -> [CheckCircle] {
    var circleArray = [CheckCircle]()

    for subview in v.subviews as! [UIView] {
        circleArray += getSubviewsOfView(subview)

        if subview is CheckCircle {
            circleArray.append(subview as! CheckCircle)
        }
    }

    return circleArray
}

Solution 2

Based on Aaron Brager and ullstrm answers

Details

• Xcode 9.1, Swift 4,
• Xcode Version 10.3 (10G8), Swift 5

Solution

extension UIView {

    class func getAllSubviews<T: UIView>(from parenView: UIView) -> [T] {
        return parenView.subviews.flatMap { subView -> [T] in
            var result = getAllSubviews(from: subView) as [T]
            if let view = subView as? T { result.append(view) }
            return result
        }
    }

    class func getAllSubviews(from parenView: UIView, types: [UIView.Type]) -> [UIView] {
        return parenView.subviews.flatMap { subView -> [UIView] in
            var result = getAllSubviews(from: subView) as [UIView]
            for type in types {
                if subView.classForCoder == type {
                    result.append(subView)
                    return result
                }
            }
            return result
        }
    }

    func getAllSubviews<T: UIView>() -> [T] { return UIView.getAllSubviews(from: self) as [T] }
    func get<T: UIView>(all type: T.Type) -> [T] { return UIView.getAllSubviews(from: self) as [T] }
    func get(all types: [UIView.Type]) -> [UIView] { return UIView.getAllSubviews(from: self, types: types) }
}

Usage sample

var allViews = UIView.getAllSubviews(from: simpleView)
func printResult(with text: String) {
    print("\n==============================================")
    print("\(text):\n\(allViews.map { $0.classForCoder } )")
}
printResult(with: "UIView.getAllSubviews(from: simpleView)")

allViews = UIView.getAllSubviews(from: simpleView) as [UILabel]
printResult(with: "UIView.getAllSubviews(from: simpleView) as [UILabel]")

allViews = UIView.getAllSubviews(from: simpleView, types: [UIStackView.self, UILabel.self])
printResult(with: "UIView.getAllSubviews(from: simpleView, types: [UIStackView.self, UILabel.self])")

allViews = simpleView.getAllSubviews()
printResult(with: "simpleView.getAllSubviews()")

allViews = simpleView.getAllSubviews() as [UILabel]
printResult(with: "simpleView.getAllSubviews() as [UILabel]")

allViews = simpleView.get(all: UILabel.self)
printResult(with: "simpleView.get(all: UILabel.self)")

allViews = simpleView.get(all: [UIStackView.self, UILabel.self])
printResult(with: "simpleView.get(all: [UIStackView.self, UILabel.self])")

Output of the sample

==============================================
UIView.getAllSubviews(from: simpleView):
[UILabel, UIButton, UILabel, UILabel, UILabel, UIStackView]

==============================================
UIView.getAllSubviews(from: simpleView) as [UILabel]:
[UILabel, UILabel, UILabel, UILabel]

==============================================
UIView.getAllSubviews(from: simpleView, types: [UIStackView.self, UILabel.self]):
[UILabel, UILabel, UILabel, UILabel, UIStackView]

==============================================
simpleView.getAllSubviews():
[UILabel, UIButton, UILabel, UILabel, UILabel, UIStackView]

==============================================
simpleView.getAllSubviews() as [UILabel]:
[UILabel, UILabel, UILabel, UILabel]

==============================================
simpleView.get(all: UILabel.self):
[UILabel, UILabel, UILabel, UILabel]

==============================================
simpleView.get(all: [UIStackView.self, UILabel.self]):
[UILabel, UILabel, UILabel, UILabel, UIStackView]

Storyboard of the sample

Other info

Also, I suggest to work with weak references. Array with weak references to objects

Solution 3

You can implement it simply by extending UIView and defining the following functions.

Swift4 Code

extension UIView {
    func findViews<T: UIView>(subclassOf: T.Type) -> [T] {
        return recursiveSubviews.compactMap { $0 as? T }
    }

    var recursiveSubviews: [UIView] {
        return subviews + subviews.flatMap { $0.recursiveSubviews }
    }
}

Usage

findViews(subclassOf: UILabel.self)
findViews(subclassOf: CheckCircle.self)

Solution 4

My approach with swift 3 and generics!

private func getSubviewsOf<T: UIView>(view: UIView) -> [T] {
    var subviews = [T]()

    for subview in view.subviews {
        subviews += getSubviewsOf(view: subview) as [T]

        if let subview = subview as? T {
            subviews.append(subview)
        }
    }

    return subviews
}

To fetch all UILabel's in a view hierarchy, just do this:

let allLabels: [UILabel] = getSubviewsOf(view: theView)

View more solutions

Comments

[Kenji Crosland]

Thank you. It worked. I decided to change one small part: if let viewToAppend = subview as? CheckCircle { circleArray.append(viewToAppend as CheckCircle) }

[Aaron Brager]

@KenjiCrosland If you want to do that, I'd just do if let subview = subview as? CheckCircle and append(subview). No need to rename it or cast inside the if let scope.

[nayem]

Best answer with great usage of generics!

[nodebase]

This is epic. Thank you.