Swift: Get all subviews of a specific type and add

问题:

I have a custom class of buttons in a UIView that I'd like to add to an array so that they're easily accessible. Is there a way to get all subviews of a specific class and add it to an array in Swift?

回答1:

The filter function using the is operator can filter items of a specific class.

let myViews = view.subviews.filter{$0 is MyButtonClass}

MyButtonClass is the custom class to be filtered for.

回答2:

Here you go

    extension UIView {

    /** This is the function to get subViews of a view of a particular type 
*/
    func subViews<T : UIView>(type : T.Type) -> [T]{
        var all = [T]()
        for view in self.subviews {
            if let aView = view as? T{
                all.append(aView)
            }
        }
        return all
    }


/** This is a function to get subViews of a particular type from view recursively. It would look recursively in all subviews and return back the subviews of the type T */
        func allSubViewsOf<T : UIView>(type : T.Type) -> [T]{
            var all = [T]()
            func getSubview(view: UIView) {
                if let aView = view as? T{
                all.append(aView)
                }
                guard view.subviews.count>0 else { return }
                view.subviews.forEach{ getSubview(view: $0) }
            }
            getSubview(view: self)
            return all
        }
    }

You can call it like

let allSubviews = view.allSubViewsOf(type: UIView.self)
let allLabels = view.allSubViewsOf(type: UILabel.self)

回答3:

To do this recursively (I.e. fetching all subview's views aswell), you can use this generic function:

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)

回答4:

I can't test it right now but this should work in Swift 2:

view.subviews.flatMap{ $0 as? YourView }

Which returns an array of YourView

Here's a tested, typical example, to get a count:

countDots = allDots!.view.subviews.flatMap{$0 as? Dot}.count

回答5:

If you want to update/access those specific subviews then use this,

for (index,button) in (view.subviews.filter{$0 is UIButton}).enumerated(){
    button.isHidden = false
}

回答6:

From Swift 4.1, you can use new compactMap (flatMap is now depcrecated): https://developer.apple.com/documentation/swift/sequence/2950916-compactmap (see examples inside)

In your case, you can use:

let buttons:[UIButton] = stackView.subviews.compactMap{ $0 as? UIButton }

And you can execute actions to all buttons using map:

let _ = stackView.subviews.compactMap{ $0 as? UIButton }.map { $0.isSelected = false }

回答7:

So many of the answers here are unnecessarily verbose or insufficiently general. Here's how to get all subviews of a view, at any depth, that are of any desired class:

extension UIView {
    func subviews<T:UIView>(ofType WhatType:T.Type) -> [T] {
        var result = self.subviews.compactMap {$0 as? T}
        for sub in self.subviews {
            result.append(contentsOf: sub.subviews(ofType:WhatType))
        }
        return result
    }
}

How to use:

let arr = myView.subviews(ofType: MyButtonClass.self)

回答8:

func allSubViews(views: [UIView]) {
    for view in views {
        if let tf = view as? UITextField {
             // Do Something
        }
        self.allSubViews(views: view.subviews)
    }
}

self.allSubViews(views: self.view.subviews)

回答9:

For this case, I think we could use Swift's first.where syntax, which is more efficient than filter.count, filter.isEmpty.

Because when we use filter, it will create a underlying array, thus not effective, imagine we have a large collection.

So just check if a view's subViews collection contains a specific kind of class, we can use this

let containsBannerViewKind = view.subviews.first(where: { $0 is BannerView }) != nil

which equivalent to: find me the first match to BannerView class in this view's subViews collection. So if this is true, we can carry out our further logic.

Reference: https://github.com/realm/SwiftLint/blob/master/Rules.md#first-where

回答10:

Let me post my variation of this) but this, finds the first of T

extension UIView {

    func firstSubView<T: UIView>(ofType type: T.Type) -> T? {
        var resultView: T?
        for view in subviews {
            if let view = view as? T {
                resultView = view
                break
            }
            else {
                if let foundView = view.firstSubView(ofType: T.self) {
                    resultView = foundView
                    break
                }
            }
        }
        return resultView
    }
}