Helper to capture the last tapped bar button item in an UIKit or SwiftUI app. SwiftUI uses UIBarButtonItem under the hood in iOS 14 with the new toolbar API. Anchoring popovers from UIKit requires this as sender.

BarButtonWatcher.swift

/// Helper to capture the last tapped bar button item in an UIKit or SwiftUI app.
final class BarButtonWatcher {
    /// Singleton accessor. There can only be one currently tapped bar button item per process.
    static let shared = BarButtonWatcher()

    static private(set) weak var lastBarButtonItem: UIBarButtonItem? {
        didSet {
            // reset in next runloop
            if lastBarButtonItem != nil {
                DispatchQueue.main.async { self.lastBarButtonItem = nil }
            }
        }
    }

    init() {
        _ = try? UIApplication.shared.hook(#selector(UIApplication.sendAction(_:to:from:for:)),
        methodSignature: (@convention(c) (AnyObject, Selector, Selector, Any?, Any?, UIEvent?) -> Bool).self,
        hookSignature: (@convention(block) (AnyObject, Selector, Any?, Any?, UIEvent?) -> Bool).self) {
        store in { _self, action, target, sender, event in
            if let barButtonItem = sender as? UIBarButtonItem {
                BarButtonWatcher.lastBarButtonItem = barButtonItem
            }
            return store.original(_self, store.selector, action, target, sender, event)
            }
        }
    }
}

Requires https://github.com/steipete/InterposeKit (add via SwiftPM)