ios - 从 Firebase 下载表格 View 中的项目过多

Question

当我从不同的设备上发帖时，当前设备上的表格 View 会保留以前存在的项目，然后再次下载这些项目，包括新帖子，任何人都可以帮助我制作它，以便它只显示其中之一每一个项目？

我认为问题出在我的 downloadFromFirebase() 中。

这是我的代码:

class DisplayVC: UIViewController, UITableViewDelegate, UITableViewDataSource, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

@IBOutlet weak var captionField: RoundTextField!
@IBOutlet weak var tableView: UITableView!
@IBOutlet weak var myMainImg: roundImage!

var imageSelected = false
static var imageCache: NSCache<NSString,UIImage> = NSCache()
var posts = [Post]() // array for the posts
var imagePicker: UIImagePickerController!

@IBAction func addImageTapped(_ sender: Any) {
    present(imagePicker, animated: true, completion: nil)

}

@IBAction func logoutPressed(_ sender: Any) {
    //remove keychain and sign out of firebase
    let keychainResult = KeychainWrapper.standard.removeObject(forKey: KEY_UID)
    print("AA: ID removed from keychain: \(keychainResult)")
    try! FIRAuth.auth()?.signOut()
    performSegue(withIdentifier: "goToSignIn", sender: nil)

}
@IBAction func postBtnTapped(_ sender: Any) {
   //does this exist? or is it null? if condition is not true then it is executed
    guard let caption = captionField.text, caption != "" else {
        let alert = UIAlertController(title: "Bad Caption", message: "Caption must be entered", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .cancel, handler: nil))
        self.present(alert, animated: true, completion: nil)
        return
    }
    guard let img = myMainImg.image, imageSelected == true else {
        let alert = UIAlertController(title: "Bad Image", message: "Image must be choosen", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .cancel, handler: nil))
        self.present(alert, animated: true, completion: nil)
        return

    }
    if let imgData = UIImageJPEGRepresentation(img, 0.2){

        let imgUid = NSUUID().uuidString
        let metadata = FIRStorageMetadata()
        metadata.contentType = "image/jpeg"

        DataService.ds.REF_POST_IMAGES.child(imgUid).put(imgData, metadata: metadata, completion: { (metadata, error) in
            if error != nil{
                print("unable to upload image to Firebase storage")
            }else{
                print("GREAT SUCESS FOR IMAGE ON STORAGE")
                let downloadURL = metadata?.downloadURL()?.absoluteString
                if let url = downloadURL{
                    self.postToFireBase(imageURL: url)
                }
            }
        })
    }

}

func postToFireBase(imageURL: String){
    let post: Dictionary<String, AnyObject> = ["caption": captionField.text as AnyObject,"imageURL":imageURL as AnyObject, "likes":0 as AnyObject,"userName": userName as AnyObject]

    let firebasePost = DataService.ds.REF_POSTS.childByAutoId()
    firebasePost.setValue(post)

    captionField.text = ""
    imageSelected = false
    myMainImg.image = UIImage(named: "add-image")

    posts.removeAll()
    tableView.reloadData()
}



//cannot use the view did load for the guard method!
override func viewDidAppear(_ animated: Bool) {

}

override func viewDidLoad() {
    super.viewDidLoad()
    self.hideKeyboardWhenTappedAround()

    tableView.delegate = self
    tableView.dataSource = self

    imagePicker = UIImagePickerController()
    imagePicker.allowsEditing = true
    imagePicker.delegate = self

    posts.removeAll()
    self.downloadFromFirebase()
}

func downloadFromFirebase(){
    //"POSTS" Listener, initialize listener and it will work constantly
    DataService.ds.REF_POSTS.observe(.value, with: { (snapshot) in

        if let snapshot = snapshot.children.allObjects as? [FIRDataSnapshot]{
            for snap in snapshot{
                print("SNAP: \(snap)") // make free objects by parsing the JSON
                if let postDict = snap.value as? Dictionary<String, AnyObject>{
                    let key = snap.key
                    let post = Post(postKey: key, postData: postDict)
                    self.posts.append(post) //stick the post in the posts Array
                }

            }
        }
        self.tableView.reloadData()
    })
}

func numberOfSections(in tableView: UITableView) -> Int {
    return 1
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return posts.count //number of total posts
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let post = posts[indexPath.row]

    if let cell = tableView.dequeueReusableCell(withIdentifier: "PostCell") as? PostCell{

        if let img = DisplayVC.imageCache.object(forKey: post.imageURL as NSString){
            cell.configureCell(post: post, image: img)
            return cell
        }else{
            cell.configureCell(post: post, image: nil)
            return cell
        }
    }else{
        return PostCell()
    }

}

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
    if let image = info[UIImagePickerControllerEditedImage] as? UIImage{
     myMainImg.image = image

    }else{
        print("AA: Valid image wasn't selected")
    }
    imagePicker.dismiss(animated: true, completion: nil)
    imageSelected = true

}

func hideKeyboardWhenTappedAround() {
    let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(dismissKeyboard))
    view.addGestureRecognizer(tap)
}

func dismissKeyboard() {
    view.endEditing(true)
}
}

Answer 1

试试这个:

包含在之后

let post = Post(postKey: key, postData: postDict)

以下内容:

if !posts.contains(post) {
    self.post.append(post)
}

让我知道它是否有效!