iOS Swift. How to get all subviews of UIView

The following task - get all subviews of provided view. There are several solutions how to do this.

1. Simple one - only first level of embedding

Just go through all subviews of view and add them to subview array. But in this solution only subviews on first level of embedding will be added to array.

func getSubviewsOfView(view: UIView) -> [UIView] {
    var subviewArray = [UIView]()
    for subview in view.subviews {
        subviewArray.append(subview)
    }
    return subviewArray
}

let subviews = self.getSubviewsOfView(view: self.view)

2. Getting all subviews - all embedded subviews (Recursively)

If we need to reach all subviews at all (all sub children) we must use recursive approach.

func getSubviewsOfView(view: UIView) -> [UIView] {
    var subviewArray = [UIView]()
    if view.subviews.count == 0 {
        return subviewArray
    }
    for subview in view.subviews {
        subviewArray += self.getSubviewsOfView(view: subview)
        subviewArray.append(subview)
    }
    return subviewArray
}

3. Getting all subviews of special type

If we need to collect only subviews of special class.  There we check every subview.

func getSubviewsOfView(view: UIView) -> [CustomView] {
        var subviewArray = [CustomView]()
        for subview in view.subviews {
            subviewArray += self.getSubviewsOfView(view: subview)
            if let subview = subview as? CustomView {
                subviewArray.append(subview)
            }
        }
        return subviewArray
    }

4. Getting all subviews using Generics - Getting subviews of any provided type

How can we improve method above. We can make it using Generics and after that it will collect subviews of provided type.

func getSubviewsOfView<T: UIView>(view: UIView) -> [T] {
    var subviewArray = [T]()
    if view.subviews.count == 0 {
        return subviewArray
    }
    for subview in view.subviews {
        subviewArray += self.getSubviewsOfView(view: subview) as [T]
        if let subview = subview as? T {
            subviewArray.append(subview)
        }
    }
    return subviewArray
}

Example of usage Generics function.

let allLabels: [UILabel] = self.getSubviewsOfView(view: self.view)
let allViews: [UIView] = self.getSubviewsOfView(view: self.view)

5. Generics and forEach loop

Also we can replace standard for loop with forEach loop

func getSubviewsOfView<T: UIView>(view: UIView) -> [T] {
    var subviewArray = [T]()
    guard view.subviews.count>0 else { return subviewArray }
    view.subviews.forEach{
        subviewArray += self.getSubviewsOfView(view: $0) as [T]
        if let subview = $0 as? T{
            subviewArray.append(subview)
        }
    }
    return subviewArray
}

6. Extension

But let's go further and make our solution more universal and available for all views in project.
Here we found Extension. Also here we add Bool parameter recursive for specifying do we need recursive search of subviews.

extension UIView {
    
    func getSubviewsOfView<T : UIView>(type : T.Type, recursive: Bool = false) -> [T] {
        return self.getSubviewsInner(view: self, recursive: recursive)
    }

    private func getSubviewsInner<T : UIView>(view: UIView, recursive: Bool = false) -> [T] {
        var subviewArray = [T]()
        guard view.subviews.count>0 else { return subviewArray }
        view.subviews.forEach {
            if recursive {
                subviewArray += self.getSubviewsInner(view: $0, recursive: recursive) as [T]
            }
            if let subview = $0 as? T{
                subviewArray.append(subview)
            }
        }
        return subviewArray
    }
    
}

Example of usage Extension.

let allLabels = self.view.getSubviewsOfView(type: UILabel.self, recursive: true)
let allViews = self.view.getSubviewsOfView(type: UIView.self, recursive: true)

7.Using Filter function

In swift we can use High-ordered function to filter collection. But this function will return only subviews of first embedded level. Here we getting all subviews of CustomView Type.

let allViews = self.view.subviews.filter { $0 is CustomView }