FMDB中 databaseWithPath 的使用问题

阅读fmdb的源码文件（下载地址http://github.com/ccgus/fmdb）会发现下面一段注释，里面提到的创建数据库的方法也在很多博客中被引用，但是跑代码的时候发现，文件并不会像文档中所说的那样自动去创建（哪怕是在沙盒目录下的Documents目录下也不能创建成功）

/** Create a `FMDatabase` object.

An `FMDatabase` is created with a path to a SQLite database file.  This path can be one of these three:

1. A file system path.  The file does not have to exist on disk.  If it does not exist, it is created for you.

2. An empty string (`@""`).  An empty database is created at a temporary location.  This database is deleted with the `FMDatabase` connection is closed.

3. `nil`.  An in-memory database is created.  This database will be destroyed with the `FMDatabase` connection is closed.

For example, to create/open a database in your Mac OS X `tmp` folder:

FMDatabase *db = [FMDatabase databaseWithPath:@"/tmp/tmp.db"];

Or, in iOS, you might open a database in the app's `Documents` directory:

NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];

NSString *dbPath   = [docsPath stringByAppendingPathComponent:@"test.db"];

FMDatabase *db     = [FMDatabase databaseWithPath:dbPath];

(For more information on temporary and in-memory databases, read the sqlite documentation on the subject: [http://www.sqlite.org/inmemorydb.html](http://www.sqlite.org/inmemorydb.html))

@param inPath Path of database file

@return `FMDatabase` object if successful; `nil` if failure.

*/

　　

问题出在哪了呢？一般的思路是：如果文件创建不成功，可能是路径不存在，需要手动创建路径；如果路径存在，那么就可能是创建方法出了问题。

第一种情况添加下面的代码

    if (![[NSFileManager defaultManager] fileExistsAtPath:dbPath])
    {
        [[NSFileManager defaultManager] createFileAtPath:dbPath contents:nil attributes:nil];
    }

第二种情况

找了fmdb的所有代码，没有创建文件或判空路径的操作，于是猜想，也许是注释文档写好后，功能没加（个人瞎想，不必在意）。