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,

Answer 1

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

Answer 2

Based on Vasily Bodnarchuk's, Aaron Brager's, and ullstrm's answers.

Why another one?

I personally do not like to have as [XXX] and let specific: [Type], all over but rather pass the type into function calls, e.g.

let scrollViews = view.getNestedSubviews(ofType: UIScrollView.self)
print(scrollViews) // outputs: [UIScrollView]

I also renamed All to Nested because it conveys the recursive nature of the function to the API caller better.

Details

Swift 4.x, Xcode 9.1+

Solution

extension UIView {

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

    func getNestedSubviews<T: UIView>() -> [T] {
        return UIView.getNestedSubviews(view: self) as [T]
    }
}

Usage

let scrollViews = view.getNestedSubviews(ofType: UIScrollView.self)
print(scrollViews) // outputs: [UIScrollView]

Answer 3

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
}

Answer 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)

Answer 5

the UITextField is no longer on the top layer of subviews, so I use this method:

@implementation UISearchBar (changeFont)

- (void)setFont:(UIFont *)font {
    for (UIView *v in [self subviews]) {
        if ([v isKindOfClass:[UITextField class]]) {
            UITextField *tf = (UITextField *)v;
            tf.font = font;
            UILabel *l = (UILabel *)[tf valueForKey:@"placeholderLabel"];
            l.font = font;
            break;
        } else if (v.subviews.count) {
            for (UIView *v1 in v.subviews) {
                if ([v1 isKindOfClass:[UITextField class]]) {
                    UITextField *tf = (UITextField *)v1;
                    tf.font = font;
                    UILabel *l = (UILabel *)[tf valueForKey:@"placeholderLabel"];
                    l.font = font;
                    break;
                } else if (v1.subviews.count) {
                    for (UIView *v2 in v1.subviews) {
                        if ([v2 isKindOfClass:[UITextField class]]) {
                            UITextField *tf = (UITextField *)v2;
                            tf.font = font;
                            UILabel *l = (UILabel *)[tf valueForKey:@"placeholderLabel"];
                            l.font = font;
                            break;
                        }
                    }
                }
            }
        }
    }
}

a bit long winded, but should account for the textfield moving deeper in the future

Answer 6

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)