可能涉及FMDB的崩溃可能是由于内存损坏

Question

我正在iOS模拟器上进行测试，该模拟器涉及与MapBox iOS SDK一起分发的FMDB。这是一个我抓不到的错误，我想知道我是否违反了一些我不知道的FMDB规则，或者我在某个地方内存严重损坏（但我已经将问题缩小到了几行）。下面的代码将运行到注释为"不应该在这里"的行中。注释掉下面标记的任何一行都会变成"应该在这里"。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    NSString * sql_gdb = @"/Users/t2wu/Library/Application Support/iPhone Simulator/5.1/Applications/BB193B94-2549-49DB-9BBB-C66D76743515/Library/Application Support/Poki.OfflineSpotty/fremont_spatial.gdb";
    FMDatabase * db = [FMDatabase databaseWithPath:sql_gdb];
    if ([db open]) {
        db.shouldCacheStatements = TRUE; // Correct when this line is commented out
        [self fooDB:db];
        FMResultSet * debug1 = [db executeQuery:@"SELECT id, type, state FROM payloads WHERE id=?", [NSNumber numberWithLong:2]];
        BOOL DOESFIND1 = FALSE;
        while ([debug1 next]) {
            DOESFIND1 = TRUE;
            NSLog(@"Does find."); // Should be here.
        }
        if (DOESFIND1 == FALSE) {
            NSLog(@"Does not find"); // Should not be here.
        }
    }
    return YES;
}
-(void) fooDB: (FMDatabase *)db
{
    NSLog(@"SELECT id, type, state FROM payloads WHERE id=%@", [NSNumber numberWithLong:1]);
    FMResultSet * result = [db executeQuery:@"SELECT id, type, state FROM payloads WHERE id=?", [NSNumber numberWithLong:1]];   // Correct when changed to "SELECT * FROM"  
    while ([result next]) {
        return;  // Correct when this line is commented out.
    }
    return;
}

我已经把代码放在了应用程序中：didFinishLaunchingWithOptions，这样我就可以在其他内存被破坏之前第一件事就是运行它。（如果我是正确的，这应该放在所有观点之前。）但我不知道问题出在哪里。再说一遍，把"何时纠正"这两行中的任何一行都注释掉，都会产生预期的结果。或者用SELECT *而不是SELECT id, type, state进行查询也会产生所需的结果。

Answer 1

我想评论一下，您编写数据库代码和方法fooDB的方式有点难以阅读。

尝试以下操作：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
 [self fooDB];
 return YES;
}
-(BOOL) fooDB
{
   NSString * sql_gdb = @"/Users/t2wu/Library/Application Support/iPhone Simulator/5.1/Applications/BB193B94-2549-49DB-9BBB-C66D76743515/Library/Application Support/Poki.OfflineSpotty/fremont_spatial.gdb";
   FMDatabase * db = [FMDatabase databaseWithPath:sql_gdb];
   if (![db open]) {
      NSLog(@"Could not open DB.");
      return NO;
   }    
   FMResultSet * result = [db executeQuery:@"SELECT id, type, state FROM payloads WHERE id = ?", [NSNumber numberWithLong:1]];   
  while ([result next]) {
      //DO SOMETHING HERE
  }
  [result close];
  [db close];
  return YES;
}