Question

所以我的ios应用程序有点问题。当我进入控制我的评论显示的视图控制器时，我面临内存泄漏。我正在使用IGListKit，所以任何熟悉它的人都会对这个问题有很大的帮助，但是需要帮助。这是我的newCommentsViewController，它处理从firebase中提取注释并将它们发送到数据源。

    import UIKit
    import IGListKit
    import Firebase


class NewCommentsViewController: UIViewController, UITextFieldDelegate,CommentsSectionDelegate,CommentInputAccessoryViewDelegate {
    //array of comments which will be loaded by a service function
    var comments = [CommentGrabbed]()
    var messagesRef: DatabaseReference?
    var bottomConstraint: NSLayoutConstraint?
    public let addHeader = "addHeader" as ListDiffable
    public var eventKey = ""
    //This creates a lazily-initialized variable for the IGListAdapter. The initializer requires three parameters:
    //1 updater is an object conforming to IGListUpdatingDelegate, which handles row and section updates. IGListAdapterUpdater is a default implementation that is suitable for your usage.
    //2 viewController is a UIViewController that houses the adapter. This view controller is later used for navigating to other view controllers.
    //3 workingRangeSize is the size of the working range, which allows you to prepare content for sections just outside of the visible frame.

    lazy var adapter: ListAdapter = {
        return ListAdapter(updater: ListAdapterUpdater(), viewController: self)
    }()


    // 1 IGListKit uses IGListCollectionView, which is a subclass of UICollectionView, which patches some functionality and prevents others.
    let collectionView: UICollectionView = {
        // 2 This starts with a zero-sized rect since the view isn’t created yet. It uses the UICollectionViewFlowLayout just as the ClassicFeedViewController did.
        let view = UICollectionView(frame: CGRect.zero, collectionViewLayout: UICollectionViewFlowLayout())
        // 3 The background color is set to white
        view.backgroundColor = UIColor.white
        return view
    }()

    //will fetch the comments from the database and append them to an array
    fileprivate func fetchComments(){
        comments.removeAll()
        messagesRef = Database.database().reference().child("Comments").child(eventKey)
       // print(eventKey)
        // print(comments.count)
        let query = messagesRef?.queryOrderedByKey()
        query?.observe(.value, with: { (snapshot) in
            guard let allObjects = snapshot.children.allObjects as? [DataSnapshot] else {
                return
            }
           // print(snapshot)

            allObjects.forEach({ (snapshot) in
                guard let commentDictionary = snapshot.value as? [String: Any] else{
                    return
                }
                guard let uid = commentDictionary["uid"] as? String else{
                    return
                }
                UserService.show(forUID: uid, completion: { (user) in
                    if let user = user {
                        let commentFetched = CommentGrabbed(user: user, dictionary: commentDictionary)
                        commentFetched.commentID = snapshot.key
                        let filteredArr = self.comments.filter { (comment) -> Bool in
                            return comment.commentID == commentFetched.commentID
                        }
                        if filteredArr.count == 0 {
                            self.comments.append(commentFetched)

                        }
                        self.adapter.performUpdates(animated: true)
                    }else{
                        print("user is null")

                    }
                    self.comments.sort(by: { (comment1, comment2) -> Bool in
                        return comment1.creationDate.compare(comment2.creationDate) == .orderedAscending
                    })
                    self.comments.forEach({ (comments) in
                    })
                })

            })

        }, withCancel: { (error) in
            print("Failed to observe comments")
        })

        //first lets fetch comments for current event
    }

    //allows you to gain access to the input accessory view that each view controller has for inputting text
    lazy var containerView: CommentInputAccessoryView = {
        let frame = CGRect(x: 0, y: 0, width: view.frame.width, height: 50)
        let commentInputAccessoryView = CommentInputAccessoryView(frame:frame)
        commentInputAccessoryView.delegate = self
        return commentInputAccessoryView
    }()


    @objc func handleSubmit(for comment: String?){
        guard let comment = comment, comment.count > 0 else{
            return
        }

        let userText = Comments(content: comment, uid: User.current.uid, profilePic: User.current.profilePic!,eventKey: eventKey)
        sendMessage(userText)
        // will clear the comment text field
        self.containerView.clearCommentTextField()
    }


    @objc func handleKeyboardNotification(notification: NSNotification){

        if let userinfo = notification.userInfo {

            if let keyboardFrame = (userinfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue{

                self.bottomConstraint?.constant = -(keyboardFrame.height)

                let isKeyboardShowing = notification.name == NSNotification.Name.UIKeyboardWillShow

                self.bottomConstraint?.constant = isKeyboardShowing ? -(keyboardFrame.height) : 0
                if isKeyboardShowing{
                    let contentInset = UIEdgeInsetsMake(0, 0, (keyboardFrame.height), 0)
                    collectionView.contentInset = UIEdgeInsetsMake(0, 0, (keyboardFrame.height), 0)
                    collectionView.scrollIndicatorInsets = contentInset
                }else {
                    let contentInset = UIEdgeInsetsMake(0, 0, 0, 0)
                    collectionView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0)
                    collectionView.scrollIndicatorInsets = contentInset
                }


                UIView.animate(withDuration: 0, delay: 0, options: UIViewAnimationOptions.curveEaseOut, animations: {
                    self.view.layoutIfNeeded()
                }, completion: { (completion) in
                    if self.comments.count > 0  && isKeyboardShowing {
                        let item = self.collectionView.numberOfItems(inSection: self.collectionView.numberOfSections - 1)-1
                        let lastItemIndex = IndexPath(item: item, section: self.collectionView.numberOfSections - 1)
                        self.collectionView.scrollToItem(at: lastItemIndex, at: UICollectionViewScrollPosition.top, animated: true)


                    }
                })
            }
        }
    }

    override var inputAccessoryView: UIView? {
        get {
            return containerView
        }
    }

    override var canBecomeFirstResponder: Bool {
        return true
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        collectionView.frame = CGRect.init(x: 0, y: 0, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height-40)
        view.addSubview(collectionView)
        collectionView.alwaysBounceVertical = true
        adapter.collectionView = collectionView
        adapter.dataSource = self
        NotificationCenter.default.addObserver(self, selector: #selector(handleKeyboardNotification), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(handleKeyboardNotification), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
        collectionView.register(CommentCell.self, forCellWithReuseIdentifier: "CommentCell")
//        collectionView.register(CommentHeader.self, forCellWithReuseIdentifier: "HeaderCell")
        collectionView.keyboardDismissMode = .onDrag
        navigationItem.title = "Comments"
        self.navigationItem.hidesBackButton = true
        let backButton = UIBarButtonItem(image: UIImage(named: "icons8-Back-64"), style: .plain, target: self, action: #selector(GoBack))
        self.navigationItem.leftBarButtonItem = backButton
    }

    @objc func GoBack(){
        print("BACK TAPPED")
        self.dismiss(animated: true, completion: nil)
    }

    //look here
    func CommentSectionUpdared(sectionController: CommentsSectionController){
        print("like")
        self.fetchComments()
        self.adapter.performUpdates(animated: true)
    }
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        fetchComments()
        tabBarController?.tabBar.isHidden = true
        //submitButton.isUserInteractionEnabled = true

    }
    //viewDidLayoutSubviews() is overridden, setting the collectionView frame to match the view bounds.
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        //    collectionView.frame = view.bounds
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

extension NewCommentsViewController: ListAdapterDataSource {
    // 1 objects(for:) returns an array of data objects that should show up in the collection view. loader.entries is provided here as it contains the journal entries.
    func objects(for listAdapter: ListAdapter) -> [ListDiffable] {
        let items:[ListDiffable] = comments
        //print("comments = \(comments)")
        return items
    }




    // 2 For each data object, listAdapter(_:sectionControllerFor:) must return a new instance of a section controller. For now you’re returning a plain IGListSectionController to appease the compiler — in a moment, you’ll modify this to return a custom journal section controller.
    func listAdapter(_ listAdapter: ListAdapter, sectionControllerFor object: Any) -> ListSectionController {
        //the comment section controller will be placed here but we don't have it yet so this will be a placeholder
//        if let object = object as? ListDiffable, object === addHeader {
//            return CommentsHeaderSectionController()
//        }
        let sectionController = CommentsSectionController()
        sectionController.delegate = self

        return sectionController
    }

    // 3 emptyView(for:) returns a view that should be displayed when the list is empty. NASA is in a bit of a time crunch, so they didn’t budget for this feature.
    func emptyView(for listAdapter: ListAdapter) -> UIView? {
        let view = UIView()
        view.backgroundColor = UIColor.white
        return view
    }
}

extension NewCommentsViewController {
    func sendMessage(_ message: Comments) {
        ChatService.sendMessage(message, eventKey: eventKey)

    }
}

我使用仪器和调试器图形工具进行了一些调试，它似乎指向我的commentsSectionController

import UIKit
import IGListKit
import Foundation
import Firebase

protocol CommentsSectionDelegate: class {
    func CommentSectionUpdared(sectionController: CommentsSectionController)
}
class CommentsSectionController: ListSectionController,CommentCellDelegate {
    weak var delegate: CommentsSectionDelegate? = nil
    var comment: CommentGrabbed?
    let userProfileController = ProfileeViewController(collectionViewLayout: UICollectionViewFlowLayout())
    var eventKey: String?
    var dummyCell: CommentCell?
    override init() {
        super.init()
        // supplementaryViewSource = self
        //sets the spacing between items in a specfic section controller
        inset = UIEdgeInsets(top: 5, left: 0, bottom: 0, right: 0)
    }
    // MARK: IGListSectionController Overrides
    override func numberOfItems() -> Int {
        return 1
    }

具体这个功能在这里

    override func sizeForItem(at index: Int) -> CGSize {
        let frame = CGRect(x: 0, y: 0, width: collectionContext!.containerSize.width, height: 50)
        dummyCell = CommentCell(frame: frame)
        dummyCell?.comment = comment
        dummyCell?.layoutIfNeeded()
        let targetSize =  CGSize(width: collectionContext!.containerSize.width, height: 55)
        let estimatedSize = dummyCell?.systemLayoutSizeFitting(targetSize)
        let height = max(40+8+8, (estimatedSize?.height)!)
        return  CGSize(width: collectionContext!.containerSize.width, height: height)

    }

    override var minimumLineSpacing: CGFloat {
        get {
            return 0.0
        }
        set {
            self.minimumLineSpacing = 0.0
        }
    }

    override func cellForItem(at index: Int) -> UICollectionViewCell {
        guard let cell = collectionContext?.dequeueReusableCell(of: CommentCell.self, for: self, at: index) as? CommentCell else {
            fatalError()
        }
        //  print(comment)
        cell.comment = comment
        cell.delegate = self
        return cell
    }
    override func didUpdate(to object: Any) {
        comment = object as? CommentGrabbed
    }
    override func didSelectItem(at index: Int){
    }

    func optionsButtonTapped(cell: CommentCell){
        print("like")

        let comment = self.comment
        _ = comment?.uid

        // 3
        let alertController = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)

        // 4
        if comment?.uid != User.current.uid {
            let flagAction = UIAlertAction(title: "Report as Inappropriate", style: .default) { _ in
                ChatService.flag(comment!)

                let okAlert = UIAlertController(title: nil, message: "The post has been flagged.", preferredStyle: .alert)
                okAlert.addAction(UIAlertAction(title: "Ok", style: .default))
                self.viewController?.present(okAlert, animated: true, completion: nil)
            }
            let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
            let replyAction = UIAlertAction(title: "Reply to Comment", style: .default, handler: { (_) in
                //do something here later to facilitate reply comment functionality
                print("Attempting to reply to user \(comment?.user.username) comment")

            })
            alertController.addAction(replyAction)
            alertController.addAction(cancelAction)
            alertController.addAction(flagAction)
        }else{
            let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
            let deleteAction = UIAlertAction(title: "Delete Comment", style: .default, handler: { _ in
                ChatService.deleteComment(comment!, (comment?.eventKey)!)
                let okAlert = UIAlertController(title: nil, message: "Comment Has Been Deleted", preferredStyle: .alert)
                okAlert.addAction(UIAlertAction(title: "Ok", style: .default))
                self.viewController?.present(okAlert, animated: true, completion: nil)
                self.onItemDeleted()

            })
            alertController.addAction(cancelAction)
            alertController.addAction(deleteAction)

        }
        self.viewController?.present(alertController, animated: true, completion: nil)

    }
    func onItemDeleted() {
        delegate?.CommentSectionUpdared(sectionController: self)
    }
    func handleProfileTransition(tapGesture: UITapGestureRecognizer){
        userProfileController.user = comment?.user
        if Auth.auth().currentUser?.uid != comment?.uid{
                    self.viewController?.present(userProfileController, animated: true, completion: nil)
        }else{
            //do nothing

        }


    }

    deinit {
        print("CommentSectionController class removed from memory")
    }


}

这是我在调试器图形工具中看到的屏幕截图，即使我离开屏幕并检查调试器工具那些块仍在那里。

所以我的问题是，有没有人看到任何我看不到的功能。我真的想修复这个内存泄漏。除此之外，当我使用手机时，这种内存泄漏似乎并不明显，但是当我使用我的模拟器时，这是一个巨大的内存泄漏....任何见解都非常感谢

Answer 1

一些事情：

DatabaseReference由ViewController拥有的查询观察者正在捕获self（您的视图控制器）。这使得所有权圈子永远不会让对方deinit。这称为retain cycle。

将[unowned self]或[weak self]添加到完成功能块中，如下所示：

query?.observe(.value, with: { [weak self] (snapshot) in
   // your code...
}

我在这里使用了weak，因为query是可选的。

当您不再需要通知观察员时，请致电NotificationCenter.default.removeObserver(self)。

我的库的无耻插件：考虑Typist来管理UIKit中的键盘，它避免了与NotificationCenter的任何交互，并且非常容易设置和使用。

Answer 2

在viewWillDisappear方法

中删除您的通知观察者

override func viewWillDisappear(animated: Bool) {
    NSNotificationCenter.defaultCenter().removeObserver(self)
}

Answer 3

你应该在闭包中使用弱或无主参考，如下所示

query?.observe(.value, with: { [unowned self] (snapshot) in

}

Answer 4

我相信你应该用[unowned self]（或weak）重写这个闭包：

UserService.show(forUID: uid, completion: { [unowned self] user in }

正如@Dhiru所提到的，你应该删除所有通知观察者。

ViewController中的内存泄漏

4 个答案: