Does introspect cause memory leak?

[okmyself]

@crayment When I use introspect in a struct containing a viewModel, the deinit function in the viewModel never executes.
Version: Master branch on github (2022-8-25), I downloaded this to fix #140, but found this issue instead.

[okmyself]

After modifying to the following code, the memory leak problem seems to be solved.

#if canImport(UIKit)
import UIKit
import SwiftUI

/// Introspection UIView that is inserted alongside the target view.
@available(iOS 13.0, *)
public class IntrospectionUIView: UIView {
    
    var moveToWindowHandler: (() -> Void)?
    
    required init() {
        super.init(frame: .zero)
        isHidden = true
        isUserInteractionEnabled = false
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override public func didMoveToWindow() {
        super.didMoveToWindow()
        moveToWindowHandler?()
    }
}

/// Introspection View that is injected into the UIKit hierarchy alongside the target view.
/// After `updateUIView` is called, it calls `selector` to find the target view, then `customize` when the target view is found.
@available(iOS 13.0, tvOS 13.0, macOS 10.15.0, *)
public struct UIKitIntrospectionView<TargetViewType: UIView>: UIViewRepresentable {
    
    /// Method that introspects the view hierarchy to find the target view.
    /// First argument is the introspection view itself, which is contained in a view host alongside the target view.
    let selector: (IntrospectionUIView) -> TargetViewType?
    
    /// User-provided customization method for the target view.
    let customize: (TargetViewType) -> Void
    
    public init(
        selector: @escaping (IntrospectionUIView) -> TargetViewType?,
        customize: @escaping (TargetViewType) -> Void
    ) {
        self.selector = selector
        self.customize = customize
    }
    
    public func makeUIView(context: UIViewRepresentableContext<UIKitIntrospectionView>) -> IntrospectionUIView {
        let view = IntrospectionUIView()
        view.accessibilityLabel = "IntrospectionUIView<\(TargetViewType.self)>"
        view.moveToWindowHandler = {
            DispatchQueue.main.async {
                guard let targetView = selector(view) else {
                    return
                }
                customize(targetView)
            }
        }
        return view
    }

    /// When `updateUiView` is called after creating the Introspection view, it is not yet in the UIKit hierarchy.
    /// At this point, `introspectionView.superview.superview` is nil and we can't access the target UIKit view.
    /// To workaround this, we wait until the runloop is done inserting the introspection view in the hierarchy, then run the selector.
    /// Finding the target view fails silently if the selector yield no result. This happens when `updateUIView`
    /// gets called when the introspection view gets removed from the hierarchy.
    public func updateUIView(
        _ uiView: IntrospectionUIView,
        context: UIViewRepresentableContext<UIKitIntrospectionView>
    ) { }
    
    public static func dismantleUIView(_ uiView: IntrospectionUIView, coordinator: ()) {
        uiView.moveToWindowHandler = nil
    }
}
#endif

[crayment]

Thanks for reporting that! If you could open a pull request with that change I would put my support behind it and pull it into my fork. This is not my repo though so I would not be able to merge it here.

[okmyself]

Thank you. I will try it.

[okmyself]

Thanks for reporting that! If you could open a pull request with that change I would put my support behind it and pull it into my fork. This is not my repo though so I would not be able to merge it here.

@crayment I have completed my pull requests. Do I need to do anything else?

[crayment]

Thanks or doing that! That should be all - but in my experience in might be a while before it gets reviewed/merged unfortunately.

[plaps153]

This really works. It solved my problem and should be merged!

[davdroman]

@okmyself @crayment is this still a problem? I'm happy to reopen #163 and get it merged if this issue is still ongoing.

[davdroman]

@okmyself please comment via the GitHub web interface as GitHub does a terrible job at rendering email responses.

[okmyself]

@okmyself please comment via the GitHub web interface as GitHub does a terrible job at rendering email responses.

@davdroman This issue was introduced by bug fix #153. The version displayed on Github still has issues, but the current official version does not have this problem. I have also discovered another problem: In some cases, UIView does not call moveToWindowHandler, so the moveToWindowHandler call in updateUIView must be preserved.

UIKitIntrospectionView.swift

#if canImport(UIKit)
import UIKit
import SwiftUI

/// Introspection UIView that is inserted alongside the target view.
@available(iOS 13.0, *)
public class IntrospectionUIView: UIView {
    
    var moveToWindowHandler: (() -> Void)?
    
    required init() {
        super.init(frame: .zero)
        isHidden = true
        isUserInteractionEnabled = false
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override public func didMoveToWindow() {
        super.didMoveToWindow()
        moveToWindowHandler?()
    }
}

/// Introspection View that is injected into the UIKit hierarchy alongside the target view.
/// After `updateUIView` is called, it calls `selector` to find the target view, then `customize` when the target view is found.
@available(iOS 13.0, tvOS 13.0, macOS 10.15.0, *)
public struct UIKitIntrospectionView<TargetViewType: UIView>: UIViewRepresentable {
    
    /// Method that introspects the view hierarchy to find the target view.
    /// First argument is the introspection view itself, which is contained in a view host alongside the target view.
    let selector: (IntrospectionUIView) -> TargetViewType?
    
    /// User-provided customization method for the target view.
    let customize: (TargetViewType) -> Void
    
    public init(
        selector: @escaping (IntrospectionUIView) -> TargetViewType?,
        customize: @escaping (TargetViewType) -> Void
    ) {
        self.selector = selector
        self.customize = customize
    }
    
    public func makeUIView(context: UIViewRepresentableContext<UIKitIntrospectionView>) -> IntrospectionUIView {
        let view = IntrospectionUIView()
        view.accessibilityLabel = "IntrospectionUIView<\(TargetViewType.self)>"
        view.moveToWindowHandler = {
            DispatchQueue.main.async {
                guard let targetView = selector(view) else {
                    return
                }
                customize(targetView)
            }
        }
        return view
    }

    /// When `updateUiView` is called after creating the Introspection view, it is not yet in the UIKit hierarchy.
    /// At this point, `introspectionView.superview.superview` is nil and we can't access the target UIKit view.
    /// To workaround this, we wait until the runloop is done inserting the introspection view in the hierarchy, then run the selector.
    /// Finding the target view fails silently if the selector yield no result. This happens when `updateUIView`
    /// gets called when the introspection view gets removed from the hierarchy.
    public func updateUIView(
        _ uiView: IntrospectionUIView,
        context: UIViewRepresentableContext<UIKitIntrospectionView>
    ) {
        uiView.moveToWindowHandler?()
    }
    
    /// Fix memory leak issue
    public static func dismantleUIView(_ uiView: IntrospectionUIView, coordinator: ()) {
        uiView.moveToWindowHandler = nil
    }
}
#endif

[davdroman]

@okmyself okay I understand. Would you be willing to put forth a PR? If so I'll merge it right away. Otherwise I can do it when I get some spare time, but I'd appreciate if you could do it as I have lots of other issues to go through on this repo. Regardless: thank you for your response and sample code!