Firebase使用Facebook后FirebaseSimpleLogin没有触发firebase observeEventType？

1 回答

• 4

  我终于弄清楚发生了什么，这是因为我对UIViewController消息回调和CFRunLoop的错误假设 .

  我的问题中的代码示例是从我的真实代码中提取出来的，以删除多余的调用，但事实证明我删除的部分实际上是罪魁祸首 . 我编写了一个函数来登录并通过使用运行循环等到现场成功或失败（而不是稍后在块中接收响应）：

  -(bool)loginUsingFacebookReturningError:(NSError**)error andUser:(FAUser**)user
  {
      __block NSError *errorTemp;
      __block FAUser  *userTemp;
  
      [self loginUsingFacebookWithCompletionBlock:^(NSError *error, FAUser *user) {
          errorTemp = error;
          userTemp = user;
  
          CFRunLoopStop(CFRunLoopGetCurrent());
      }];
  
      CFRunLoopRun(); // needs a timeout or way for the user to cancel but I haven't implemented it yet
  
      if(error) *error = errorTemp;
      if(user) *user = userTemp;
  
      return !errorTemp && userTemp;
  }
  
  -(void)loginUsingFacebookWithCompletionBlock:(void (^)(NSError* error, FAUser* user))block
  {
      FirebaseSimpleLogin *authClient = [[FirebaseSimpleLogin alloc] initWithRef:self.firebase];
  
      [authClient loginToFacebookAppWithId:kFacebookAppID permissions:@[@"email"]
          audience:ACFacebookAudienceOnlyMe
           withCompletionBlock:^(NSError *error, FAUser *user) {
  
               if (error != nil) {
                   // There was an error logging in
                   NSLog(@"facebook error");
  
                   block(error, nil);
               } else {
                   // We have a logged in facebook user
                   NSLog(@"facebook logged in");
  
                   [authClient checkAuthStatusWithBlock:block];
               }
           }];
  }
  

  这被称为：

  NSError *error;
  FAUser  *user;
  bool    success = [self loginUsingFacebookReturningError:&error andUser:&user];
  

  loginUsingFacebookReturningError工作的方式是，它调用loginUsingFacebookWithCompletionBlock，它会像往常一样触发loginToFacebookAppWithId和checkAuthStatusWithBlock消息，但后来我开始运行循环 . 运行循环允许处理在后台进行，即使主线程在CFRunLoopRun（）上暂停，直到完成块调用CFRunLoopStop（） .

  What I hadn't realized is that run loops continue to process the application's messages in the background. 所以当我认为程序流已在viewDidLoad中停止时，它实际上已经继续并调用了viewWillAppear，这是我调用observeEventType的地方（因为我假设在程序到达时验证将完成） .

  这创建了一个race condition，其中程序在Facebook和Firebase进行身份验证期间附加了observeEventType回调 . 90％的时间，身份验证在调用observeEventType之前完成，但有10％的时间存在延迟或其他网络延迟，并且提前调用observeEventType .

  我通过将FirebaseSimpleLogin代码移动到故事板中自己的视图控制器来修复问题，并使用完成块将segue启动到安装observeEventType回调的下一个视图控制器 .

  So to summarize: the solution is to call FirebaseSimpleLogin's authentication, and then AFTER it has finished and the completion block is done, call observeEventType. Otherwise Firebase's rules will deny your request to see data that's only visible to authenticated users (which is correct).

  这是最终的代码，未经测试但是方法作品：

  // only global for illustration purposes, should really go in a singleton or AppDelegate, or be passed through the segue to the next view controller
  Firebase    *gFirebase;
  
  // LoginViewController (root view controller in storyboard)
  - (void)viewDidLoad
  {
      [super viewDidLoad];
  
      gFirebase = [[Firebase alloc] initWithUrl:@"https://xxxxx.firebaseio.com/"];
  
      FirebaseSimpleLogin *authClient = [[FirebaseSimpleLogin alloc] initWithRef:gFirebase];
  
      [authClient loginToFacebookAppWithId:kFacebookAppID permissions:@[@"email"]
                  audience:ACFacebookAudienceOnlyMe
                  withCompletionBlock:^(NSError *error, FAUser *user) {
  
          if (error != nil) {
              // There was an error logging in
              NSLog(@"facebook error");
          } else {
              // We have a logged in facebook user
              NSLog(@"facebook logged in");
  
              [authClient checkAuthStatusWithBlock:^(NSError* error, FAUser* user) {
                  if (error != nil) {
                      // Oh no! There was an error performing the check
                      NSLog(@"auth error");
                  } else if (user == nil) {
                      // No user is logged in
                      NSLog(@"auth not logged in");
                  } else {
                      // There is a logged in user
                      NSLog(@"auth logged in");
  
                      // segue to the chat view controller
                      [self performSegueWithIdentifier:@"segueToViewController" sender:self];
                  }
              }];
          }
      }];
  }
  
  // ViewController (destination of segueToViewController)
  - (void)viewDidLoad
  {
      [super viewDidLoad];
  
      [gFirebase observeEventType:FEventTypeChildAdded withBlock:^(FDataSnapshot *snapshot) {
          NSLog(@"%@", snapshot.value);
  
          // Add the chat message to the array.
          [self.chat addObject:snapshot.value];
          // Reload the table view so the new message will show up.
          [self.tableView reloadData];
  
          [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:([self.tableView numberOfRowsInSection:0] - 1) inSection:0] atScrollPosition:UITableViewScrollPositionBottom animated:YES];
      }];
  }
  

  回复于 2024-04-25T13:41:22+08:00