Exceptions alternative

[Exotic_Devel]

From what I've been reading, Qt does not use exceptions. So what would be the way to capture errors from some Qt classes? For example QFile.

[SGaist]

Hi,

Operation that might fail in Qt are generally in the form of bool methodThatMightFail() so you would check whether the method is successful and if not check the error/errorString method. Some more advanced classes are using a dedicated error class like QSqlError.

Hope it helps

[Chris Kawa]

In most cases Qt uses error codes or other meaningful return values like null pointers. For example if file can't be opened for whatever reason QFile::open() will return false.

Often you can also query for the result of some operation. An example of that is "QNetworkReply::error()":http://qt-project.org/doc/qt-5/qnetworkreply.html#error

If an operation is in some sense detached from the point of invocation (eg. asynchronous) Qt also emits signals. An example of that is "QNetworkAccessManager::sslErrors":http://qt-project.org/doc/qt-5/qnetworkaccessmanager.html#sslErrors

In rare cases you can also pass an optional variable that will be filled with the result of an operation. An example of that is "QString::toInt()":http://qt-project.org/doc/qt-5/qstring.html#toInt

If unsure how specific class handles an error refer to the docs. They are usually clear about it.