C++ QT 5.0 - 内置日志记录？
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QT 5.0 - Built in Logging?
提问by rreeves
I was doing some research on Qt 5.0 Logging and it appears to have built in classes for logging. I'm having trouble finding an example. I have located the classes i believe are relevant here.
我正在对 Qt 5.0 Logging 进行一些研究，它似乎内置了用于日志记录的类。我很难找到一个例子。我在这里找到了我认为相关的课程。
I can see roughly how to create the QMessageLogger Object from the documentation, but how can I create a log file and append to it?
我可以从文档中大致了解如何创建 QMessageLogger 对象，但是如何创建日志文件并将其附加到其中？
回答by Huy
By default using qDebug(), qWarning(), etc will allow you to log information out to the console.
默认情况下，使用 qDebug()、qWarning() 等将允许您将信息注销到控制台。
#include <QtDebug>
qDebug() << "Hello world!";
QMessageLogger is designed to leverage special C++ macros (e.g. function, line, file)
QMessageLogger 旨在利用特殊的 C++ 宏（例如函数、行、文件）
QMessageLogger(__FILE__, __LINE__, 0).debug() << "Hello world!";
In Qt5 the message logger is used behind the scenes since qDebug() is a macro that will eventually instantiate an instance of QMessageLogger. So I'd just go with using the regular qDebug().
在 Qt5 中，消息记录器在幕后使用，因为 qDebug() 是一个宏，最终会实例化 QMessageLogger 的实例。所以我只会使用常规的 qDebug()。
The QMessageLogContext contains what I'd consider as "meta-data", i.e. the file, line number, etc that the qDebug() statement it was called from. Normally you'd concern yourself with the log-context if you're defining your own QtMessageHandler (see qInstallMessageHandler()).
QMessageLogContext 包含我认为是“元数据”的内容，即从中调用 qDebug() 语句的文件、行号等。如果您定义自己的 QtMessageHandler（请参阅 qInstallMessageHandler()），通常您会关心日志上下文。
The message handler allows for more control of the logging mechanism - like sending logging information to a custom logging server or even to a file.
消息处理程序允许对日志机制进行更多控制——比如将日志信息发送到自定义日志服务器甚至文件。
As provided in the Qt Documentation, creating a custom message handler is simple:
正如 Qt 文档中提供的那样，创建自定义消息处理程序很简单：
void myMessageHandler(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
std::cout << msg.toStdString();
}
Check out better examples and explanations here.
