从firebase数据库检索数据：代码没有进入完成块或错误块 [英] Retrieving data from firebase database: code didn't go into the completion block or an error block

问题描述

我试图从数据库中检索数据，但是我的代码没有进入完成块或错误块。我不想从用户进行任何身份验证身份验证，并从应用程序保存数据库中的数据。只是想从数据库中检索数据。我的数据库结构是这样的

< img src =https://i.stack.imgur.com/IUF5j.pngalt =在这里输入图片描述>

这里是代码

   - （void）viewDidLoad {
 [FIRDatabase database] .persistenceEnabled = YES; 
 [self referenceFromURL：@https://project-8326407164650950213.firebaseio.com]; （FIRDatabaseReference *）referenceFromURL：（NSString *）databaseUrl {
 
 commentsRef = [[FIRDatabase database] referenceFromURL：databaseUrl]; 
 
  - 
返回commentsRef; 
 
 
 $ b  - （void）viewWillAppear：（BOOL）animated 
 {
 [[commentRef child：@Hello] 
 observeEventType：FIRDataEventTypeValue 
 withBlock：^（FIRDataSnapshot * snapshot）{
 NSDictionary * post = snapshot.value; 
 
} withCancelBlock：^（NSError * error）{
 NSLog（@％@，error.description）; 
}]; 
 
 
 
 
 
 $ b 
告诉我在代码中缺少的是什么。 
解决方案
 
  NSString * strUrl = [NSString stringWithFormat：@https：// project- 8326407164650950213.firebaseio.com]; 
 FIRDatabaseReference * ref = [[FIRDatabase database] referenceFromURL：strUrl]; 
 [ref observeSingleEventOfType：FIRDataEventTypeValue withBlock：^（FIRDataSnapshot * _Nonnull snapshot）{
 NSDictionary * post = snapshot.value; 
 NSLog（@％@，post）; 
}]; 
  
 
 
 
 
 
以下代码将从Firebase获取您的数据。 / li> 
 
只有你的代码有问题，你写了[commentsRef child：@Hello]。使用直接urlreference获取数据。
 
I am trying to retrieve data  from database but my code didn't go into the completion block or an error block. I didn't want any auth authentication from user and save data in database from an app. Just  want to retrieve data from database. My database structure is like that



Here is the code 
- (void)viewDidLoad {
    [FIRDatabase database].persistenceEnabled = YES;
    [self referenceFromURL:@"https://project-8326407164650950213.firebaseio.com"];
}
- (FIRDatabaseReference *) referenceFromURL:(NSString *)databaseUrl{

    commentsRef = [[FIRDatabase database] referenceFromURL:databaseUrl];
    return commentsRef;
}


-(void)viewWillAppear:(BOOL)animated
{
    [[commentsRef child:@"Hello"]
     observeEventType:FIRDataEventTypeValue
     withBlock:^(FIRDataSnapshot *snapshot) {
         NSDictionary * post = snapshot.value;

     }withCancelBlock:^(NSError * error){
         NSLog(@"%@",error.description);
     }];
}
Tell me what I am missing in that code. 
解决方案
        NSString *strUrl = [NSString stringWithFormat:@"https://project-8326407164650950213.firebaseio.com"];
    FIRDatabaseReference *ref = [[FIRDatabase database] referenceFromURL:strUrl];
    [ref observeSingleEventOfType:FIRDataEventTypeValue withBlock:^(FIRDataSnapshot * _Nonnull snapshot) {
        NSDictionary *post = snapshot.value;
        NSLog(@"%@",post);
    }];



Here is the code with you will get your data from Firebase.
Only problem with your code is you wrote "[commentsRef child:@"Hello"]". Use direct urlreference to fetch data.


                        
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