異步任務可以在循環中運行嗎？ （在iOS中）

Question

基本上我使用firebase來查詢用戶的'狀態'屬性，並在do/while循環中這樣做。

如果狀態屬性是空閒的，那麼我想打破循環並繼續執行其餘的方法。如果狀態屬性不是空閒的，那麼我想再次查詢一個新用戶的firebase，直到找到一個空閒用戶。

我的firebase代碼在循環外工作良好，但似乎並沒有在它內部調用。這裏是循環：

__block uint32_t rando; 
self.freedom = @"about to check"; 

do { 
//check if free 

[self checkIfFree:^(BOOL finished) { 

    if (finished) { 
     if ([self.freedom isEqualToString:@"free"]) { 
      //should break loop here 
     } 

     else if ([self.freedom isEqualToString:@"matched"]){ 

      //get another user 

      do { 
       //picking another random user from array 
       rando = arc4random_uniform(arraycount); 
      } 
      while (rando == randomIndex && rando == [self.randString intValue]); 

      self.randString = [NSString stringWithFormat:@"%u", rando]; 
      [users removeAllObjects]; 
      [users addObject:[usersArray objectAtIndex:rando]]; 
      self.freeUser = [users objectAtIndex:0]; 

      //should repeat check here but doesn't work 
     } 
     else{ 
      NSLog(@"error!"); 
     } 
    } 
    else{ 
     NSLog(@"not finished the checking yet"); 
    } 
}]; 
} while (![self.freedom isEqual: @"free"]); 

這是我的火力代碼：

-(void)checkIfFree:(myCompletion) compblock{ 

self.freeUserFB = [[Firebase alloc] initWithUrl:[NSString stringWithFormat: @"https://skipchat.firebaseio.com/users/%@", self.freeUser.objectId]]; 

[self.freeUserFB observeEventType:FEventTypeValue withBlock:^(FDataSnapshot *snapshot) 
{ 
    self.otherStatus = snapshot.value[@"status"]; 

    NSLog(@"snapshot info %@", snapshot.value); 

    if ([self.otherStatus isEqualToString:@"free"]) { 
     self.userIsFree = YES; 
     self.freedom = @"free"; 
    } 
    else{ 
     self.userIsFree = NO; 
     self.freedom = @"matched";    
    } 
    compblock(YES); 
}]; 
} 

謝謝！

Answer 1

我不知道我是否正確理解你的問題。 如果您想再次運行完成代碼，直到某些條件匹配（在這種情況下[self.freedom isEqualToString:@"free"]），你可以做以下（去除DO - 一會兒）：

void(^ myResponseBlock)(BOOL finished) =^void(BOOL finished) { 
    if (finished) { 
     if ([self.freedom isEqualToString: @"free"]) { 
      return; 
     } else if ([self.freedom isEqualToString: @"matched"]) { 
      //get another user 
      do { 
       //picking another random user from array 
       rando = arc4random_uniform(arraycount); 
      } 
      while (rando == randomIndex && rando == [self.randString intValue]); 
      self.randString = [NSString stringWithFormat: @"%u", rando]; 
      [users removeAllObjects]; 
      [users addObject:usersArray[rando]]; 
      self.freeUser = users.firstObject; 

      // Schedule another async check 
      [self checkIfFree: myResponseBlock]; 
     } else { 
      NSLog(@"error!"); 
     } 
    } else { 
     NSLog(@"not finished the checking yet"); 
    } 
}; 

[self checkIfFree: myResponseBlock];