如何使用CollectionView摆脱保留周期 [英] How to get rid of retain cycle with collectionview

问题描述

由于我认为这是collectionview和viewcontroller之间的保留周期，因此我在销毁viewcontroller时遇到了麻烦.我试图使collectionview成为一个弱变量，但是当我尝试将collectionview添加到viewcontroller时，我现在得到的是nil.如果还有另一种方法可以尝试而不是使collectionview变弱，那么我也对此持开放态度.

I am having trouble destroying viewcontrollers due what I believe to be a retain cycle between a collectionview and the viewcontroller. I tried making the collectionview a weak variable but I am now getting nil whenever I trying to add the collectionview to the viewcontroller. If there is another route to try rather than making the collectionview weak I'm open to that as well.

weak var table = UICollectionView(frame: CGRect(x: 0, y: 0, width: 0, height: 0), collectionViewLayout: UICollectionViewFlowLayout())
weak var customFlowLayout = UICollectionViewFlowLayout() //default cell spacing is 10





table?.frame = CGRect(x: 0, y: 50, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height)
table?.isHidden = true
table?.backgroundColor = UIColor.white
table?.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "customCellIdentifier")
table?.dataSource = self
table?.delegate = self
//table.rowHeight = CGFloat(100)
customFlowLayout?.minimumLineSpacing = 5 //default is 10
table?.collectionViewLayout = customFlowLayout!
self.view.addSubview(table!)  //this is the line that breaks every time

推荐答案

我看不到您提供的代码中的任何保留周期.除非某个地方传递了一个块，否则很难有一个由标准UICollectionView直接引起的保留周期.如果有的话，挂在UICollectionView上的视图控制器可能永远不会释放.

I don't see any retain cycles from the code you provided. Unless there is a block being passed somewhere, it's likely pretty difficult to have a retain cycle directly caused by a standard UICollectionView. If anything it's likely that your view controller holding onto the UICollectionView is never being released.

UICollectionView的视图控制器上的属性可能很弱，但是您需要像这样声明局部变量作为强引用(没有weak):

The property on your view controller for the UICollectionView can be weak, but you need to declare the local variable as a strong reference (no weak) like so:

class ViewController : UIViewController {
    weak var collectionView: UICollectionView?

    // Maybe in viewDidLoad()    
    let cv = UICollectionView(...)
    ...
    self.view.addSubview(cv)
    self.collectionView = cv

您的本地声明应作为强引用，否则将被分配并立即释放，因为没有任何保留.将cv添加为子视图后，它将具有来自view的强大引用.您班级的名为collectionView的属性现在可以作为弱引用，并且在取消分配视图后将释放collectionView.

Your local declaration should be a strong reference, otherwise it will be allocated and immediately released because nothing is holding onto it. Once cv is added as a subview, then it will have a strong reference from the view. Your class's property called collectionView can now be a weak reference and the collectionView will be released once the view is deallocated.

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