ios - UITableView 重复 Firebase 数据

Question

我从 Firebase 收到重复的内容，但我似乎无法弄清楚我做错了什么。在 firebase 中，我有 6 个帖子。 tableview 正在填充 6 个单元格，但所有 6 个单元格都具有相同的数据，而其他 5 个帖子不存在。

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

{
    RankingsCell *cell = [tableView dequeueReusableCellWithIdentifier:@"RankingsCell"];
    self.ref = [[FIRDatabase database] reference];
    posts = [ref child:@"posts"];

    [posts observeEventType:FIRDataEventTypeValue withBlock:^(FIRDataSnapshot *snapshot)
     {
         for (snapshot in snapshot.children)
         {
             NSString *username = snapshot.value[@"Name"];
             NSString *date = snapshot.value[@"Date"];
             NSString *combatPower = snapshot.value[@"Combat Power"];
             NSString *pokemon = snapshot.value[@"Pokemon"];
             NSString *pokemonURL = snapshot.value[@"Pokemon Image"];
             NSString *picURL = snapshot.value[@"Profile Picture"];
             int CP = [combatPower intValue];

             cell.usernameOutlet.text = username;
             cell.dateOutlet.text = date;
             cell.combatPowerLabel.text = [NSString stringWithFormat:@"COMBAT POWER: %d", CP];
             cell.pokemonLabel.text = pokemon;
             [cell downloadUserImage:picURL];
             [cell downloadPokemonImage:pokemonURL];
         }
     }
        withCancelBlock:^(NSError * _Nonnull error)
     {
         NSLog(@"%@", error.localizedDescription);
     }];
    return cell;
}

Answer 1

cellForRowAtIndex: 方法为“每个”单元格调用，因此您不应该在其中进行数据库工作，它只负责一次创建“一个”单元格。

因此，将您的 observeEventType: 调用移动到 viewDidLoad: 或 viewDidAppear: 中，例如:

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.ref = [[FIRDatabase database] reference];
    posts = [ref child:@"posts"];

    [posts observeEventType:FIRDataEventTypeValue withBlock:^(FIRDataSnapshot *snapshot)
     {
         self.allSnapshots = [NSMutableArray array];

         for (snapshot in snapshot.children)
         {
                 [self.allSnapshots addObject:snapshot];
         }

         [self.tableView reloadData]; // Refresh table view after getting data
     } // .. error ...
}

并且在 numberOfRowsForInSection:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section      
{
    return [self.allSnapshots count];
}

并且在 cellForRowAtIndex:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    RankingsCell *cell = [tableView dequeueReusableCellWithIdentifier:@"RankingsCell"];

    FIRDataSnapshot *snapshot = [self.allSnapshots objectAtIndex:indexPath.row]; 

    NSString *username = snapshot.value[@"Name"];
    NSString *date = snapshot.value[@"Date"];
    NSString *combatPower = snapshot.value[@"Combat Power"];
    NSString *pokemon = snapshot.value[@"Pokemon"];
    NSString *pokemonURL = snapshot.value[@"Pokemon Image"];
    NSString *picURL = snapshot.value[@"Profile Picture"];
    int CP = [combatPower intValue];

    cell.usernameOutlet.text = username;
    cell.dateOutlet.text = date;
    cell.combatPowerLabel.text = [NSString stringWithFormat:@"COMBAT POWER: %d", CP];
    cell.pokemonLabel.text = pokemon;
    [cell downloadUserImage:picURL];
    [cell downloadPokemonImage:pokemonURL];

    return cell;
}