[Qt-interest] 答复: connect mysql

[pengliang(彭亮)]

Hi
	This problem still exist after I modified it as your said.
Thanks
Ken


-----邮件原件-----
发件人: qt-interest-bounces+pengliang=founder.com at qt.nokia.com [mailto:qt-interest-bounces+pengliang=founder.com at qt.nokia.com] 代表 Tony Rietwyk
发送时间: 2011年9月20日 8:40
收件人: qt-interest at qt.nokia.com
主题: Re: [Qt-interest] connect mysql



> Sent: Tuesday, 20 September 2011 7:41 AM
> 
> I guess clear() is not enough or there is another query which was not cleared.
> According to documentation you have to make sure no open queries on the
> database connection when this function is called.
> For some reason it does not.
> 
> Alex
> 
> 
> Sent: Tuesday, September 13, 2011 11:32 PM
> 
> Hello
>    I don t know why application always output that information. Anybody
> could tell me why.
> 
> 
> 
> ---------------------------------    snippets
>     query.clear();
>     f5ErpDb.close();
>     f5ErpDb.removeDatabase("QODBC");
> 
>     camMysqlDb = QSqlDatabase::addDatabase("QMYSQL");
> 
> 
> -------------------    application output
> QSqlDatabasePrivate::removeDatabase: connection
> 'qt_sql_default_connection' is still in use, all queries will cease to work.
>      QSqlDatabasePrivate::addDatabase: duplicate connection name
> 'qt_sql_default_connection', old connection removed.

Hi Alex & Pengliang, 

QSqlDatabase.close says that it invalidates any queries - it says nothing about them being open or valid at the time.  So you need to use block structuring to release the objects entirely: 

{
	QSqlDatabase f5ErpDb = QSqlDatabase::addDatabase("QODBC");
	...
	{
		QSqlQuery query(f5ErpDb);
		...
	}

	f5ErpDb.close();
	QSqlDatabase::removeDatabase("QODBC");
}
{
	QSqlDatabase camMysqlDb = QSqlDatabase::addDatabase("QMYSQL");
	...
	// Etc...
}

Encapsulating each block in its own method is the obvious recommendation! 

Hope that helps, 

Tony.


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