Firebase,如何返回句柄,以便我可以调用removeObserver? [英] Firebase, how do I return a handle so that I can call removeObserver?
本文介绍了Firebase,如何返回句柄,以便我可以调用removeObserver?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
let databaseRef = FIRDatabase.database()。reference()
let查询= databaseRef.child(palettes)。queryOrdered(byChild:UserDefaults.standard.string(forKey:UserTypeState)!)。queryEqual(toValue:modifiedColor.hexValue())
//将值更改为颜色的值。
query.observe(.childAdded,with:{(snapshot)in
let URL = snapshot.childSnapshot(forPath:URL)。value as!String
self。 URLArrayString.append(URL)
self.collectionView?.reloadData()//在数字和所有URL被提取后重新加载数据
self.noResultsLabel.isHidden = true
})
当我调用特定的观察者时,如何检索句柄, viewDidDissapear? 当您调用 observe
它返回注册观察者的句柄。 b
$ b
您将此句柄传递给 removeObserverWithHandle()
以删除观察者。
<$ ($。$ b $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $)
query.removeObserverWithHandle (处理)
Here's my observe event code:
let databaseRef = FIRDatabase.database().reference()
let query = databaseRef.child("palettes").queryOrdered(byChild: UserDefaults.standard.string(forKey: "UserTypeState")!).queryEqual(toValue: modifiedColor.hexValue())
// Change the value to the value of the color.
query.observe(.childAdded, with: { (snapshot) in
let URL = snapshot.childSnapshot(forPath: "URL").value as! String
self.URLArrayString.append(URL)
self.collectionView?.reloadData() //Reloads data after the number and all the URLs are fetched
self.noResultsLabel.isHidden = true
})
How do I retrieve the handle when that particular observer is called so that I can remove it when viewDidDissapear?
解决方案
When you call observe
it returns a handle to the registered observer.
You pass this handle to removeObserverWithHandle()
to remove the observer.
let handle = query.observe(.childAdded, with: { (snapshot) in
....
})
And then:
query.removeObserverWithHandle(handle)
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