FMDatabaseQueue死锁

Question

我正在使用FMDatabaseQueue并将其设置为单身

static FMDatabaseQueue* sharedDatabase;

+ (FMDatabaseQueue *)sharedDatabase
{
  if (sharedDatabase == nil) sharedDatabase = [FMDatabaseQueue databaseQueueWithPath:DATABASE_PATH];

  return sharedDatabase;
}

当我像这样调用inDatabase方法时，它会导致死锁......

[[UserData sharedDatabase] inDatabase:^(FMDatabase *db) {
  FMResultSet * rs = [db executeQuery:@"SELECT id FROM table1"];
  if([rs next]) {
    [[NSNotificationCenter defaultCenter] postNotificationName:kNotification1 object:aObject userInfo:@{@"key":@1}]; 
  }else{
    [[NSNotificationCenter defaultCenter] postNotificationName:kNotification1 object:aObject userInfo:@{@"key":@0}]; 
  }
  [rs close];
}];

---

另一个控制器观察通知

- (void)update:(NSNotification *)notification
{
  NSNumber *key = [notification.userInfo objectForKey:@"key"];
  if ([key isEqual:@1]){
    [[UserData sharedDatabase] inDatabase:^(FMDatabase *db) {
      [db executeUpdate:@"UPDATE table1 SET number = ?",1];
    }];
  }
}

任何人都有想法解决这个问题......？

Answer 1

执行查询后发送通知怎么样？

__block BOOL result;

[[UserData sharedDatabase] inDatabase:^(FMDatabase *db) {
  FMResultSet * rs = [db executeQuery:@"SELECT id FROM table1"];
  result = ([rs next]) ? YES : NO;
  [rs close];
}];

[[NSNotificationCenter defaultCenter] postNotificationName:kNotification1 object:aObject userInfo:@{@"key":@result}]; 

Answer 2

我不知道你究竟该做什么，但是你应该知道dataBase只能同时访问。因为FMResultSet是一个Singleton，它只能访问数据库。

所以我认为你改变了这样：

 [[UserData sharedDatabase] inDatabase:^(FMDatabase *db)  
{ 
  int  resultCount = 0
  FMResultSet * rs = [db executeQuery:@"SELECT id FROM table1"];
  if([rs next]) 
  { 
    resultCount++;
  }
  [rs close];

  [[NSNotificationCenter defaultCenter] postNotificationName:kNotification1 object:aObject userInfo:@{@"key":resultCount}];
}];

-(void)update:(NSNotification *)notification
{
  NSNumber *key = [notification.userInfo objectForKey:@"key"];
 if ([key isEqual:@1])
 {
   [[UserData sharedDatabase] inDatabase:^(FMDatabase *db)
   {
     [db executeUpdate:@"UPDATE table1 SET number = ?",1];// ?i think the sql is some thing wrong
   }];
  } 
 }